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EDC MS5 in-line injection pump

Fault diagnosis

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©
Scania CV AB 1998-03, Sweden
1 585 749
 Contents
Diagnosing faults with the General............................................................ 3
diagnostics lamp Interviewing the driver ................................... 4
Fault codes ...................................................... 4
Wiring diagrams ............................................. 4
Faults that do not generate fault codes ........... 4
Accessing the fault codes................................ 5
Erasing the fault codes.................................... 6

List of fault codes ........................................................................ 7

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Control unit connections ...................................................................... 37

Wiring diagrams Current circuit diagrams, 12 engine.............. 42

Current circuit diagrams, 14 engine.............. 49

Location of electrical components Location of components, 12 engine.............. 41

Location of components, 14 engine.............. 48

Faults that do not generate fault ...................................................................... 56

codes

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 General

EDC

Diagnosing faults with the

diagnostics lamp

• The fault code texts have been taken directly from the PC program Scania Diagnos
and are given here in their original form to avoid confusion.
• Suggestions are made in the text as to how each fault may be dealt with.
• The fault code texts conclude with references to the current circuit diagrams in the
”Wiring diagrams” section. This section also contains diagrams showing the loca-

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tions of the electrical components.
• Further information on how the EDC system is connected to the various electrical
systems in the vehicle is given in the connection diagrams in Group 16.
• Faults that do not cause fault codes to be generated are included in the section
headed ”Faults that do not generate fault codes”.

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Fault diagnosis

Interviewing the driver Wiring diagrams

Begin fault diagnosis by interviewing the The fault code texts conclude with references
driver. Try to get an overall picture of the to current circuits. These current circuits refer
problem. Ask about the following: to the current circuit diagrams in the ”Wiring
diagrams” section.
- Fault symptoms
- Under what conditions the fault arose The diagrams for the 12 and 14 engines are
- How often the fault has arisen shown individually and in unbroken sequence.
- If the warning lamp came on Each section starts with a drawing which
- If the warning lamp went out by itself shows the location of components.
- If the driver has erased fault codes
Further information as to how the EDC system
is connected to the vehicle’s electrical system is
shown in the connection diagrams in Group 16.

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Fault codes Faults that do not generate
Access all the fault codes stored in the mem-
fault codes
ory. Compare them and attempt to reach a con-
clusion as to the probable cause of the fault Although the control unit software is advanced
before taking any further action. Fault codes and anticipatory, a fault may arise which the
are stored in the order in which they were control unit cannot distinguish from something
registered. that can occur during the course of normal
operation. In such case, no fault code will be
generated; there is always a limit to how exten-
sively a function can be monitored. A table of
various faults with their symptoms and causes
is given in the section headed ”Faults that do
not generate fault codes”.
Remember that the kind of faults which can arise
in a fuel system without EDC, such as defective
injectors, can also arise in EDC vehicles.

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 Accessing the fault codes

Accessing the fault codes

The power should be switched on with the
starter key.
1 Press the diagnostics switch and count the

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number of flashes.
2 Press the switch again and count the number
of flashes. If the same code is repeated,
there is only one fault in the system. If more
than one code is shown, continue to press
the button until the first code is displayed 1 2
again. Note all the fault codes.

ED C
ATC

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1 Diagnostics switch
2 Diagnostics lamp

The long flashes (1 second) that appear first rep-

resent tens, the short flashes (0.3 second) that
follow are units.
The example to the right displays fault code 25.

A single long flash (4 seconds) means that there

are no fault codes in the memory.

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Erasing the fault codes

Erasing the fault codes

Fault codes should be erased once the fault diag-
nosis has been completed and the fault rectified.
Erasure is carried out at two different levels and
is described below.

Erasing fault codes

The following erases fault codes that are
flashed with the diagnostics lamp. However, the

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fault codes will still remain in another memory
which can only be accessed with a PC.
1 Start and switch off the engine to initiate a
shutdown test. Wait until the indicator lamp
goes out.
1 2

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2 Press and hold the diagnostics switch in the
depressed position.
3 Turn the starter key to the drive position and
wait for at least 3 seconds. Resetting is now ED C
ATC
completed.

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4 Start the engine and check that the indicator
lamp goes out.
1 Diagnostics switch
5 Press the diagnostics switch. The fault code 2 Diagnostics lamp
memory should be empty, i.e. it should give
one long flash.

Final erasure of fault codes using

a PC
After the fault diagnosis has been completed and
the fault rectified, final erasure of the fault codes
should be carried out using Scania Diagnos and
a PC. The PC erases the flashing code memory
and the PC memory in the control unit at the
same time.
A PC should also be used to erase the fault code
memory when the pre-delivery inspection has
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been carried out to ensure that the PC memory

is empty when the vehicle is delivered to the
customer.

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 List of fault codes

List of fault codes

The following is a list of those fault codes that can be generated. More detailed information about each
fault code is given in the following pages.

Fault code Cause

11 Overrevving
12 Main engine-speed sensor
13 Auxiliary engine-speed sensor
14 Coolant temperature sensor
15 Charge air temperature sensor
16 Charge air pressure sensor
21 Control for cruise control
22 Brake pedal switches
24 Throttle pedal/brake pedal

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25 Throttle pedal sensor
26 Speed signal
27 Speed signal
28 Speed signal
31 Injection timing
32 Control rack position
33 Battery voltage
34 Needle movement sensor
35 Control-rack position sensor
36 Control-rack position sensor
37 Emergency stop
41 Throttle pedal sensor
42 Throttle pedal sensor
43 CAN communication
44 Needle movement sensor
45 Needle movement sensor
46 Needle movement sensor
61 Shut-down test
62 Fuel valve
63 Driver stage
64 Supply relay
81 Control unit
82 Shut-down test
83 Control unit

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List of fault codes

Fault code 11 Overrevving

Fault: At least one of the signals for engine speed shows over
3000 rpm.
Cause: The control unit has sensed that the frequency of at
least one of the signals to pins 21 and 22 has been too high.
Comment: The signal from the main engine speed sensor or
the auxiliary engine speed sensor has shown over 3000 rpm.
The setting solenoid loses power (engine switched off) until
both engine speed signals are below 3000 rpm. The engine
then functions as normal.
The fault is caused by the driver changing to a lower gear in
an incorrect manner. It can also be caused by interference in
the engine speed signal.
Action: Check engine speed sensors, connectors and wiring.

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Current circuit, 12 engine: 38, 62
Current circuit, 14 engine: 9, 62

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 List of fault codes

Fault code 12 Main engine-speed sensor

Fault: The fault code may be generated for any of four reasons:
1 When the engine is started, the signal from the main
engine speed sensor shows a lower engine speed than the
signal from the auxiliary engine speed sensor. The speed
shown by the main engine speed sensor is below 50 rpm
while the speed shown by the auxiliary engine speed sen-
sor is above 100 rpm.
2 The signal from the main engine speed sensor shows
implausible changes in engine speed from pulse to pulse.
3 The speed shown by the signal from the main engine
speed sensor is lower than that shown by the signal from
the auxiliary engine speed sensor. The speed shown by
the auxiliary engine speed sensor is above 700 rpm. the
speed shown by the main engine speed sensor at the same
time is less than 90 % of the speed shown by the auxiliary
engine speed sensor.

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4 Every revolution of the engine gives rise to a regularly
recurring disturbance in the signal from the main engine
speed sensor.
Cause:
1 When starting the engine, the frequency of the signal to
pin 21 has been too low compared with the frequency of
the signal to pin 22.
2 The frequency of the signal to pin 21 has been too uneven.
3 The frequency of the signal to pin 21 has been too low
compared with the frequency of the signal to pin 22.
4 Every revolution of the engine has given rise to a regu-
larly recurring disturbance in the signal applied to pin 21.
Comment: As long as the fault is active, engine torque is lim-
ited. If the fault disappears, the engine functions as normal.
For safety reasons, the control unit always works on the infor-
mation from the sensor which gives the highest engine speed.
This fault code can therefore sometimes be generated for the
sensor which is actually giving the right reading.
The fault code is generated if the sensor cables are incorrectly
connected. A cable that is mistaken for another and connected
will transmit an inverted signal.
This fault can be caused by incorrect distance between sensor
and flywheel/toothed wheel.
If fault code 13 arises at the same time, that is to say both
engine speed sensors are faulty, the engine is switched off
(setting solenoid is not powered).
Action: Check engine speed sensors, connectors and wiring.
Current circuit, 12 engine: 38
Current circuit, 14 engine: 9

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List of fault codes

Fault code 13 Auxiliary engine-speed sensor

Fault: This fault code can be generated for two reasons:
1 The signal from the auxiliary engine speed sensor shows
implausible changes in engine speed from pulse to pulse.
2 The engine speed shown by the signal from the auxiliary
engine speed sensor is lower than that shown by the signal
from the main engine speed sensor. The speed shown by
the main engine speed sensor is above 700 rpm. The
speed shown by the auxiliary engine speed sensor is less
than 90 % of that shown by the main engine speed sensor.
Cause:
1 The frequency of the signal to pin 22 has been too une-
ven.
2 The frequency of the signal to pin 22 has been too low

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compared with the frequency of the signal to pin 21.
Comment: As long as the fault is active, engine torque is lim-
ited. If the fault disappears, the engine functions as normal.
For safety reasons, the control unit always works on the infor-
mation from the sensor which gives the highest engine speed.
This fault code can therefore sometimes be generated for the
sensor which is actually giving the right reading.
The fault can be caused by incorrect distance between sensor
and ring gear.
If fault code 12 arises as the same time, that is to say both
engine speed sensors are faulty, the engine is switched off
(setting solenoid looses power).
Action: Check engine speed sensors, connectors and wiring.
Current circuit, 12 engine: 62
Current circuit, 14 engine: 62

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 List of fault codes

Fault code 14 Coolant temperature sensor

Fault: Implausible signal from the coolant temperature sensor.
Cause: Voltage too low or too high between pins 53 and 13
on the control unit.
Comment: The voltage has been below 0.44 V (above
130 ˚C)or above 4.94 V (below -40 ˚C).
If the voltage is outside the permitted range, the control unit
uses a pre-programmed temperature (40 ˚C).
The engine’s ability to start in the cold will be impaired as
long as the fault is active. Idling speed is raised to 600 rpm
and cannot be adjusted.
Action: Check temperature sensor, connectors and wiring.
Current circuit, 12 engine: 17

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Current circuit, 14 engine: 17

Fault code 15 Charge air temperature sensor

Fault: Implausible signal from the charge air temperature
sensor.
Cause: Voltage too low or too high between pins 55 and 13
on the control unit.
Comment: The voltage has been below 0.44 V (above
130 ˚C)or above 4.94 V (below -40 ˚C).
If the voltage is outside the permitted range, the control unit
uses a pre-programmed temperature (40 ˚C).
As long as the fault is active, the engine will respond slower
than usual to acceleration in cold weather because the smoke
limiter is not working as it should.
Action: Check temperature sensor, connectors and wiring.
Current circuit, 12 engine: 13
Current circuit, 14 engine: 13

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List of fault codes

Fault code 16 Charge air pressure sensor

Fault: Implausible signal from charge air pressure sensor.
Cause: Voltage too low or too high to pin 36 on the control
unit.
Comment: The voltage has been below 0.33 V (0.5 bar) or
above 4.66 V (4.0 bar).
If the voltage is outside the permissible range, the control unit
uses a preprogrammed pressure (approx. 1.7 bar).
The charge air pressure sensor reads the absolute pressure in
the intake manifold, that is, it reads the surrounding air pres-
sure and the overpressure given off by the turbocharger.
Engine torque is limited as long as the fault is active.
Action: Check the charge air pressure sensor, connectors and

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wiring.
Current circuit, 12 engine: 21
Current circuit, 14 engine: 21

Fault code 21 Control for cruise control

Fault: Implausible signal from control for cruise control.
Cause: Voltage between pins 44 and 13 too low or too high.
The voltage level between the ACC, RES, RET, ON and OFF
functions may also be one that is not allowed.
Comment: As long as the fault is present, cruise control, hand
throttle and idling adjustment do not work.
The control unit interprets the voltage level as follows:
0.67-1.03 V, ON+ACC
1.50-1.89 V, ON+RES
2.37-2.82 V, ON+RET
3.20-3.57 V, ON
3.57-4.40 V, OFF
The fault code is generated if the voltage level is outside these
ranges.
Action: Check the switch, connectors and wiring.
Current circuit, 12 engine: 4
Current circuit, 14 engine: 4

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 List of fault codes

Fault code 22 Brake pedal switches

Fault: The brake pedal switches give conflicting signals
about the position of the pedal. One switch signals that the
pedal is released while the other signals that it is depressed.
Cause: Pins 24 and 43 have both been earthed at the same time
or both pins have lacked earth connection at the same time.
Comment: Both the brake pedal switches have been simulta-
neously closed or open for more than five minutes.
Cruise control, the hand throttle and idling adjustments will
not work as long as the fault is active.
This fault can be due to the switches being incorrectly
adjusted or the nut being tightened too hard so that the switch
seizes.
Action: Check switches, connectors and wiring.

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Current circuit, 12 engine: 103, 113
Current circuit, 14 engine: 103, 113

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List of fault codes

Fault code 24 Throttle pedal/brake pedal

Fault: Signals that the throttle and brake pedals are both
depressed at the same time.
Cause: Voltage too high to pin 27 at the same time as pin 24
has been earthed or pin 43 has not been earthed.
Comment: Throttle pedal and brake pedal must have been
depressed at the same time while braking more than 20 times
in a row for the fault code to be generated. The intention of
this fault code is to discover if the throttle pedal is not return-
ing properly e.g. broken return spring.
Voltage to pin 27 has been above 0.45 V.
Fault in the brake pedal switches gives fault code 22. Fault in
the throttle pedal sensor actuation switch/potentiometer gives
fault code 25.

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Action: Check the movement of the throttle pedal.
Current circuit, 12 engine: 71, 103. 113
Current circuit, 14 engine: 71, 103. 113

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 List of fault codes

Fault code 25 Throttle pedal sensor

Fault: This fault code can be generated for two reasons:
1 Implausible signal from potentiometer.
2 Implausible difference between the throttle pedal sensor’s
potentiometer and throttle actuation switch.
Cause:
1 Voltage too low or too high to pin 27.
2 Voltage too low to pin 27 at the same time as pin 39 is
earthed. Voltage too high to pin 27 at the same time as pin
39 is not earthed.
Comment:
1 Voltage has been below 0.25 V or above 4.00 V.

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2 The vehicle can be driven in emergency mode to the near-
est repair shop by means of the throttle actuation switch.
In emergency mode, idling speed is obtained when the
accelerator is released and half throttle performance when
it is fully depressed (throttle actuation switch closed). The
cruise control can be used when vehicle speed exceeds 35
km/h.
3 Voltage has either been below 0.49 V with the throttle
actuation switch closed or else it has been above 0.90 V
with the throttle actuation switch open.
4 The engine runs at slightly higher rpm than normal idling
speed. The engine does not respond to the throttle pedal.
The cruise control can be used when vehicle speed
exceeds 35 km/h.
Action: Check potentiometer. Compare potentiometer and
throttle actuation switch. Check connectors and wiring.
Current circuit, 12 engine: 71, 107
Current circuit, 14 engine: 71, 107

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List of fault codes

Fault code 26 Speed signal

Fault: Speed signal absent or implausible.
Cause: No input signal on pin 51, signal shows implausibly
high speed, signal frequency is too high or signal voltage level
is too low or too high.
Comment: The signal from the tachograph has shown a speed
above 150 km/h. Cruise control, hand throttle and idling
adjustment do not work.
When the fault is active, the control unit uses a pre-programmed
speed (15 km/h).
The fault code is generated even if a break or short circuit
occurs in the cable leading from the tachograph to the control
unit.
The voltage of the road-speed signal is an internal voltage

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level of the control unit. It cannot be read with a multimeter.
Action: Check tachograph operation on the chart or while test
driving. If the tachograph is working properly, check the wir-
ing between the tachograph and the control unit.
Current circuit, 12 engine: 89
Current circuit, 14 engine: 89

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 List of fault codes

Fault code 27 Speed signal

Fault: No speed signal or implausibly high speed.
Cause: No input signal on pin 51 or speed calculated by the
control unit is implausibly high.
Comment: The fault code is generated in the event of an open
circuit (break) in the lead between the tachograph and the con-
trol unit.
The fault code will be generated if the signal from the tacho-
graph shows a speed above 150 km/h.
On control units manufactured in January, 1998 and later, the
engine must be running for the fault code to be generated.
When the fault is active, the control unit uses a pre-programmed
speed (15 km/h).

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Cruise control, hand throttle and idling adjustment not working.
Action: Check tachograph operation on the chart or while test
driving. If the tachograph is working properly, check the wir-
ing between the tachograph and the control unit.
Current circuit, 12 engine: 89
Current circuit, 14 engine: 89

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List of fault codes

Fault code 28 Speed signal

Fault: Implausible speed signal.
Cause: The input signal frequency on pin 51 is too high, the
signal voltage level is too low or too high.
Comment: The fault code will be generated if the cable
between the tachograph and control unit is shorted to +24 V
or chassis earth.
The fault code can also be generated by external electrical
interference.
Cruise control, hand throttle and idling adjustment not working.
When the fault is active, the control unit uses a pre-pro-
grammed speed (15 km/h).
On control units manufactured in January, 1998 and later, the

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engine must be running for the fault code to be generated.
The voltage of the road-speed signal is an internal voltage
level of the control unit. It cannot be read with a multimeter.
Action: Check tachograph operation on the chart or while test
driving. If the tachograph is working properly, check the wir-
ing between the tachograph and the control unit.
Current circuit, 12 engine: 89
Current circuit, 14 engine: 89

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 List of fault codes

Fault code 31 Injection timing

Fault: Injection timing cannot be set correctly.
Cause: Implausible deviation in time between the input signal
on pin 32 (needle movement sensor) and the input signal on
pin 21 (main engine speed sensor).
Comment: This fault could be due to:
1 Low fuel pressure or poor filling (air in fuel) of injection
pump.
2 Injection pump seizing (prestroke sleeve, prestroke shaft
or setting solenoid).
3 Opening pressure too low on the injector having the nee-
dle movement sensor (on exhaust braking).
4 Faulty basic setting of pump or fault in pump transmission.

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5 Control unit’s driver stage has stopped working.
Engine torque is limited as long as the fault is active.
The fault code can only arise in engines with variable injec-
tion timing. The fault may arise together with fault codes 34,
44 and 45.
Action: Look for air leakage into the fuel system, both on the
low pressure and high pressure sides.
Check that the overflow valve is working.
Check that the fuel valve does not have a defective contact.
Check the injection timing setting solenoid, connectors and
wiring.
Check the basic setting of the pump and mechanical
components.
Current circuit, 12 engine: -
Current circuit, 14 engine: 9, 67, 37

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List of fault codes

Fault code 32 Control rack position

Fault: The control rack cannot be correctly set. The position
of the control rack measured by the control rack position sen-
sor (actual value) does not correspond to the position the con-
trol unit is attempting to set (nominal value).
Cause: The output signal on pins 1 and 2 (setting solenoid,
fuel volume) does not correspond to the input signal on pins 9,
10 and 11 (control rack position sensor).
Comment: This fault can be due to seizure of the control rack
or a defective setting solenoid.
On vehicles manufactured in March 1997 and earlier, the
most common cause of the fault is shorting in the wiring
between engine and cab. Improved wiring was introduced
in March, 1997.
Power is removed from the setting solenoid (engine switched

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off). If the fault disappears by itself, power must be switched
off and on (shutdown test) before the control unit interprets
function as normal.
Control units manufactured in April, 1996 and later are of
improved design and not as likely to generate fault code 32.
Action: Check setting solenoid, connectors and wiring. Check
control rack movement.
In the case of trouble associated with fault code 32 and sudden
engine failure on vehicles manufactured in March 1997 and
earlier, try fitting the wiring of improved design as an initial
remedy.
Current circuit, 12 engine: 44
Current circuit, 14 engine: 44

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 List of fault codes

Fault code 33 Battery voltage

Fault: Control unit has detected battery voltage below 9 V.
Cause: Input voltage on pins 15 and 16 too low.
Comment: This fault can arise when starting from cold with
poor batteries.
Action: Check battery and alternator. Check connectors and
wiring.
Current circuit, 12 engine: 33
Current circuit, 14 engine: 33

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List of fault codes

Fault code 34 Needle movement sensor

Fault: This fault code can be generated for two reasons:
1 Implausible resistance in circuit for needle movement
sensor.
2 Implausible deviations in needle movement sensor signal
compared with engine speed.
Cause:
1 Control unit has sensed that the resistance in the circuit
between pins 32 and 17 has been too low or too high.
2 The frequency of the signal to pin 32 has deviated from
the engine speed signals to pin 21.
Comment: As long as the fault is present, engine torque will
be limited.

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This fault can only arise in engines with variable injection
timing. The fault may arise together with fault code 31.
Air in the fuel system could be the cause of the nozzle needle
not opening as it should, e.g. after replacement of the fuel fil-
ter.
The fault could be due to a binding nozzle needle.
If the warning lamp comes on during exhaust braking, the
injector with the needle movement sensor probably has too
low opening pressure.
Action: Check needle movement sensor, connectors and wiring.
Look for air leakage into the fuel system, both on the low
pressure and high pressure sides.
Current circuit, 12 engine: -
Current circuit, 14 engine: 67

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 List of fault codes

Fault code 35 Control-rack position sensor

Fault: Defective contact, control rack position sensor signal.
Cause: The control unit has sensed that the signals on pins 9,
10 or 11 have been too uneven.
Comment: The fault code will be generated if at least 3 defec-
tive contacts occur within 10 seconds. If the fault disappears by
itself, power must be switched off and on before the indicator
lamp goes out. The fault code should provide a reminder that
the vehicle should be taken to a workshop for repair.
This fault code can arise together with fault code 36.
Action: Check control rack position sensor, connectors and
wiring.
Look for breaks in the wiring. Switch on the power. Erase the
fault code memory, shake connectors and check to see if the

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fault code is regenerated.
Current circuit, 12 engine: 45
Current circuit, 14 engine: 45

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List of fault codes

Fault code 36 Control-rack position sensor

Fault: Implausible signal from control rack position sensor.
Cause: Voltage level on pins 9, 10 or 11 too high or too low.
Comment: On control units manufactured in April, 1996 and
earlier, the setting solenoid will be without power (engine is
switched off).
On control units manufactured in April 1996 and later, the
engine will run at a speed slightly above that of normal idling
speed. The vehicle can be driven in emergency mode to the
nearest workshop. The engine does not respond to the throttle
pedal.
This fault can arise together with fault code 35.
Action: Check control rack position sensor, connectors and
wiring.

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Look for breaks in the wiring. Switch on the power. Erase the
fault code memory, shake connectors and check to see if the
fault code is regenerated.
Current circuit, 12 engine: 45
Current circuit, 14 engine: 45

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 List of fault codes

Fault code 37 Emergency stop

Fault: Signal from emergency stop switch.
Cause: Pin 25 on the control unit has been earthed.
Comment: On a stationary vehicle the engine is switched off.
While the vehicle is being driven, the engine will run at idling
speed. This ensures that the power steering system will con-
tinue to be operative.
The fault code is generated every time the emergency stop
switch is used. In most cases this will not indicate a fault in
the system. Should there be a cable fault between the control
unit and the emergency stop switch, however, the fault code
could be useful.
The fault code is generated only by control units manufac-
tured in April, 1996 and earlier. Control units manufactured in
April, 1996 and later do not generate a fault code when the

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emergency stop switch is used.
Action: Check the switch, connectors and wiring.
Current circuit, 12 engine: 94
Current circuit, 14 engine: 94

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List of fault codes

Fault code 41 Throttle pedal sensor

Fault: Implausible signal from the accelerator pedal sensor’s
potentiometer.
Cause: Input voltage on pin 27 too low or too high.
Comment: The voltage has been lower than 0.25 V or higher
than 4.00 V.
Throttle opening is reduced to idling when the fault arises,
and engine torque is limited.
The vehicle can be driven in emergency mode to the nearest
repair shop by means of the throttle actuation switch. In emer-
gency mode, idling speed is obtained when the throttle pedal
is released and half throttle performance when it is fully
depressed (throttle actuation switch closed). The cruise con-
trol can be used when vehicle speed exceeds 35 km/h.

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Action: Check the potentiometer, connectors and wiring.
Current circuit, 12 engine: 71
Current circuit, 14 engine: 71

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 List of fault codes

Fault code 42 Throttle pedal sensor

Fault: Implausible deviation between throttle pedal sensor
potentiometer and throttle actuation switch.
Cause: Input voltage on pin 27 too low and pin 39 earthed.
Input voltage on pin 27 too high and pin 39 not earthed.
Comment: The voltage has been lower than 0.49 V at the
same time as the throttle actuation switch has been closed.
Alternatively, the voltage has been higher than 0.90 V at the
same time as the throttle actuation switch has been open.
The engine runs slightly faster than at normal idling speed.
The engine does not respond to the throttle pedal. The cruise
control can be used when vehicle speed exceeds 35 km/h.
Engine torque is limited.
Action: Check potentiometer. Compare potentiometer and

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throttle activation switch. Check connectors and wiring.
Current circuit, 12 engine: 71, 107
Current circuit, 14 engine: 71, 107

Fault code 43 CAN communication

Fault: Fault in CAN communications circuit.
Cause: Internal fault in control unit.
Comment: The fault does not affect the operation of the
engine, but the other control units receive no engine informa-
tion. Other systems (e.g. ABS/TC, Opticruise) cannot take
over control of engine operation.
Action: Replace the control unit.
Current circuit, 12 engine: -
Current circuit, 14 engine: -

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List of fault codes

Fault code 44 Needle movement sensor

Fault: There have been more pulses from the needle move-
ment sensor than there should be for a given engine speed.
Cause: The frequency of the signal on pin 32 differs from the
engine speed signal applied to pin 21.
Comment: As long as the fault is present, engine torque will
be limited.
This fault can only arise in engines with variable injection
timing. The fault may arise together with fault code 31.
If the warning lamp comes on during exhaust braking, the
injector with the needle movement sensor probably has too
low opening pressure.
Action: Check needle movement sensor, connectors and wiring.

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Look for air leakage into the fuel system both on the low pres-
sure and high pressure sides.
Current circuit, 12 engine: -
Current circuit, 14 engine: 67

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 List of fault codes

Fault code 45 Needle movement sensor

Fault: There have been fewer pulses from the needle move-
ment sensor than there should be for a given engine speed.
Cause: The frequency of the signal on pin 32 differs from the
engine speed signal applied to pin 21.
Comment: As long as the fault is present, engine torque will
be limited.
This fault can only arise in engines with variable injection
timing. The fault may arise together with fault code 31.
Air in the fuel system could be the cause of the nozzle needle not
opening as it should, e.g. after replacement of the fuel filter.
The fault could be due to a binding nozzle needle.
Action: Check needle movement sensor, connectors and wiring.

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Check the injectors.
Current circuit, 12 engine: -
Current circuit, 14 engine: 67

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List of fault codes

Fault code 46 Needle movement sensor

Fault: Implausible resistance in the needle movement sensor
circuit.
Cause: Control unit has sensed that the resistance in the cir-
cuit between pins 32 and 17 has been too low or too high.
Comment: As long as the fault is present, engine torque will
be limited.
The fault code can only occur on engines with adjustable
injection timing.
Action: Check needle movement sensor, connectors and wiring.
Current circuit, 12 engine: -
Current circuit, 14 engine: 67

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 List of fault codes

Fault code 61 Shut-down test

Fault: Control unit has been interrupted before shutdown test
is completed.
Cause: Voltage to pins 15 and 16 has disappeared too early.
Comment: The shutdown test entails the control unit carrying
out an operational test after power has been switched off using
the key.
Engine torque will be limited if the shutdown test is inter-
rupted ten times in a row. As soon as the control unit succeeds
in carrying out a test without interruption, the fault will be
considered remedied.
The engine should always be switched off with the key. If
there is a battery master switch in the vehicle, it must not be
switched off until the indicator lamp has gone out.

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Action: Check that the warning lamp comes on for a short
time after power is switched off using the key.
Check connectors and wiring to pins 15, 16 and 46 on the con-
trol unit. Power supply may be interrupted if extra equipment
has been connected.
Current circuit, 12 engine: 32
Current circuit, 14 engine: 32

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List of fault codes

Fault code 62 Fuel valve

Fault: Engine speed does not drop sufficiently quickly when
the engine is switched off.
Cause: The frequency of the engine speed signals to pins 21
and 22 does not decrease sufficiently after power is removed
from pin 47.
Comment: Engine speed should decrease by at least 150 rpm
in 4 s.
Power is cut to the setting solenoid (engine switched off).
Next time the engine is started, torque is limited. If engine
speed drops sufficiently quickly once when the engine is
switched off, normal torque is resumed.
A possible fault cause is air in the fuel system or internal leak-
age in the fuel valve.

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This fault can arise together with fault code 63.
Action: Check that fuel valve power supply disappears imme-
diately when power is switched off using the key.
When engine speed has dropped to 350 rpm, the fuel valve is
once again powered. The valve is then powered until the shut-
down test is complete, i.e. the indicator lamp goes out.
Look for air leakage into the fuel system in the piping
between the fuel valve and feed pump. Check the overflow
valve.
Current circuit, 12 engine: 27, 39, 57, 62
Current circuit, 14 engine: 9, 27, 57, 62

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 List of fault codes

Fault code 63 Driver stage

Fault: Break or shorting in the circuit controlled by the con-
trol unit’s driver stage.
Cause: Break or short circuit to earth in the cable to pin 14.
Comment: Fuel valve shuts and the engine stops. If there is a
faulty contact, the engine runs irregularly.
If the fault disappears by itself, the power must be switched
off and on (shutdown test) before the control unit will con-
sider the function to be normal.
Fault can arise together with fault code 62.
Action: Check connectors, wiring and fuel valve.
Current circuit, 12 engine: 57
Current circuit, 14 engine: 57

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List of fault codes

Fault code 64 Supply relay

Fault: Power supply to the control unit despite the fact that
the starter key is set to locking position.
Cause: Voltage to pins 15 and 16 despite the fact that voltage
has disappeared on pin 47.
Comment: Power has not been cut to the supply relay after
the shutdown test is complete.
The indicator lamp remains on even though the power is off.
Engine operation is not affected and the engine can be restarted.
If the indicator lamp is on, the supply relay must first be
removed before the connector for the control unit can be
disconnected.
Action: Remove the supply relay and see if the warning lamp
goes out. If it goes out, the relay is not working or the cable to

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pin 46 is shorted to earth. If the lamp stays lit, the wiring to
pins 15 and 16 is shorted to +24 V.
Current circuit, 12 engine: 27, 33
Current circuit, 14 engine: 27, 33

Fault code 81 Control unit

Fault: Internal fault in the control unit.
Cause: The control unit’s two microprocessors have lost
contact with each other.
Comment: The setting solenoid looses power (engine
switched off).
Action: Replace the control unit.
Current circuit, 12 engine: -
Current circuit, 14 engine: -

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 List of fault codes

Fault code 82 Shut-down test

Fault: The control unit has discovered a fault during the
shutdown test. The position of the control rack does not
correspond to the preprogrammed position.
Cause: The output signal on pins 1 and 2 (setting solenoid,
fuel volume) does not correspond to the input signal on pins 9,
10 and 11 (control rack position sensor).
Comment: During the shutdown test, the control unit guides
the control rack out to a preprogrammed position and allows
the position sensor to read this. Power is then interrupted to
the setting solenoid.
If the control unit discovers any faults during this test, engine
torque is limited the next time the engine is started.
If fault code 82 arises together with any of fault codes 32, 35
and 36, the fault is probably outside the control unit.

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However, if fault code 82 arises on its own, this indicates an
internal fault in the control unit.
Action: Check if there are other fault codes such as 32, 35 and
36. If there are, take action on these first. Code 82 on its own
means that the control unit must be changed.
Current circuit, 12 engine: 42
Current circuit, 14 engine: 42

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List of fault codes

Fault code 83 Control unit

Fault: Internal fault in the control unit.
Cause: Control unit has discovered that the fault code mem-
ory is not working correctly.
Comment: Fault does not affect engine operation.
Action: Erase the fault code memory and check that the fault
code is not regenerated. If the fault code returns, change the
control unit.
Current circuit, 12 engine: -
Current circuit, 14 engine: -

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 Control unit connections

Control unit connections

The control unit is connected to the other EDC

systems in the vehicle via a 55-pin connector.

37 19
55

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19
55

37

18
36
54

17
35
53

16
34
52

15
33
51

14
32
50

12 13
31
49

30
47 48

11
29

10
46

28

9
45

27

8
44

26

7
43

25

6
42

24

5
41

23

4
40

22

3
21
38 39

100 296
20

Control unit connector

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Control unit connections

24 Input signal from brake pedal switch 2.

When earthed, the pin is interpreted by
1 Setting solenoid for fuel supply. the control unit as depressed brake pedal.
2 Setting solenoid for fuel supply. 25 Input signal for emergency stop. The pin
3 Setting solenoid for injection timing. shuts down the engine when earthed.

4 Setting solenoid for injection timing. 26 Input signal from clutch pedal switch.
When earthed, the pin is interpreted by the
5 Not used. control unit as depressed clutch pedal.
6 Not used. 27 Input signal from potentiometer in throttle
pedal sensor. A signal voltage is applied to
7 Not used. the pin which varies according to how
much the throttle pedal is depressed.
8 Not used.
28 Not connected (output signal for engine
9 Input signal from control rack position
speed).
sensor’s measuring coil.
29 PWM signal. Output signal for throttle
10 Input signal from control rack position
actuation.

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sensor’s reference coil.
30 CAN communication, L cable.
11 Supply to control rack position sensor.
31 CAN communication, H cable.
12 Not used.
32 Input signal from needle movement
13 Earthing of sensor.
sensor.
14 Power supply +24 V to fuel valve.
33 Power supply (+5 V) to charge air pres-
15 Power supply +24 V from the supply sure sensor.
relay to the control unit.
34 Input signal for torque limiter 2. When
16 Power supply +24 V from the supply earthed, the pin gives the ”Torque limiter
relay to the control unit. 2” function. If pin 35 is earthed at the
same time, the ”Torque limiter 3” func-
17 Earthing of sensor. tion will be obtained instead.
18 Earthing the control unit to the frame. 35 Input signal for torque limiter 1. When
earthed, the pin gives the ”Torque limiter
19 Earthing the control unit to the frame. 1” function. If pin 34 is earthed at the
20 Input signal (+24 V) from the diagnos- same time, the ”Torque limiter 3” func-
tics switch. Output signal (+24 V) for tion will be obtained instead.
activating the diagnostics lamp and 36 Input signal from charge air pressure
indicator lamp. sensor.
21 Input signal from the main engine speed 37 Not used.
sensor.
38 Not used.
22 Input signal from the auxiliary engine
speed sensor. 39 Input signal from throttle actuation
switch. When earthed, the pin is inter-
23 Input signal for limited hand throttle. preted by the control unit as depressed
When earthed, the pin gives the ”Limited throttle pedal.
hand throttle” function. If pin 41 is
earthed at the same time, the ”Fixed 40 Input signal for disengagement of cruise
engine speed” function will be obtained control. +24 V on the pin disengages the
instead. cruise control.

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 Control unit connections

41 Input signal for raised idling. When

earthed, the pin gives the ”Raised idling”
function. If pin 23 is earthed at the same
time, the ”Fixed engine speed” function
will be obtained instead.
42 Input signal for idling request. +24 V on
the pin gives idling speed.
43 Input signal from brake pedal switch 1. A
broken earth connection is interpreted by
the control unit as depressed brake pedal.
44 Input signal from control for cruise con-
trol. The control unit senses the voltage
level across pins 44 and 13.
45 Power supply (+5 V) to potentiometer in
throttle pedal sensor.
46 Output signal for activating the supply
relay. The pin earths the relay.

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47 Input signal (+24 V) from the starter lock
(key in the drive position).
48 Diagnostics cable K.
49 Diagnostics cable L.
50 Not connected ex works. Input signal for
speed limiter 2, +24 V applied to the pin
activates speed limiter 2.
51 Speed signal from tachograph output D3.
52 PWM signal. Input signal for engine
control.
53 Input signal from coolant temperature
sensor. The control unit senses the volt-
age level across pins 53 and 13.
54 Not used.
55 Input signal from charge air temperature
sensor. The control unit senses the volt-
age level across pins 5 and 13.

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Wiring diagrams

Wiring diagrams

• The section dealing with the 12 engine begins

with a drawing showing the locations of the
electrical components.
• The component drawing is diagrammatic. It
applies to both left-hand and right-hand drive
vehicles.
• The component drawing is followed by wiring
diagrams, which are marked with current cir-
cuit serial numbers. Use the current circuit ref-
erences in the list of fault codes to find the
right diagram and the components in question.
• The section covering the 14 engine is laid out

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in the same way.
• The diagrams include the component names,
e.g. E12. The full names of the components
are given in Group 16 of the Workshop Man-
ual, as also are the test readings, if any.

Changes in the wiring diagrams:

• 12 engine, current circuit 37: on vehicles
manufactured in January, 1998 and later,
cables C2-11 have been moved to C2-14.
• 14 engine, current circuit 39: on vehicles
manufactured in January, 1998 and later,
cables C2-11 have been moved to C2-14.
Corresponding changes may have been carried
out on earlier vehicles.

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 Wiring diagrams

Location of components,
12 engine

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Wiring diagrams

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 Wiring diagrams

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Wiring diagrams

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 Wiring diagrams

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Wiring diagrams

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 Wiring diagrams

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Wiring diagrams

Location of components,
14 engine

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 Wiring diagrams

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Wiring diagrams

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 Wiring diagrams

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Wiring diagrams

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 Wiring diagrams

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Wiring diagrams

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 Wiring diagrams

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Faults that do not generate fault codes

Faults that do not generate fault codes

Symptom Cause/Action

The engine has poor tractive power, The charge air pressure sensor is clogged. It then reacts less
output and torque. promptly to changes in the charge air pressure. The result is
that the engine seems to respond tardily when the throttle
pedal is depressed. No fault code is generated because the
signal from the sensor always remains within the permissi-
ble limits.
Air leakage into fuel lines on the low pressure side or leak-
ing overflow valve.
Low supply pressure from feed pump. The feed pump
should give a pressure of 3-4 bar.

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Cables to the charge air pressure sensor that have been
inverted can emit a constant pressure signal within the lim-
its permitted.

Black smoke on acceleration. The charge air pressure sensor is stuck and giving a charge
air pressure that is consistently too high.
Cables to the charge air pressure sensor that have been
inverted can emit a constant pressure signal within the
limits permitted.

Poor engine performance. Incorrect injection timing set on flywheel.

The cruise control doesn’t work. The clutch pedal switch is inoperative. Pin 26 is earthed.
+24 V to pin 40.

The engine runs at idling speed only. +24 V to pin 42.

The engine doesn’t start. Fault in power supply to pins 15 and 16.
Break in cable to pin 46 or 47.

The engine races slightly when the The brake pedal or clutch pedal switch opens too late.
cruise control is disengaged with the
brake or clutch pedal.

The cruise control doesn’t disengage The clutch pedal switch is inoperative. In consequence, pin
with the clutch pedal. 26 is not earthed when the pedal is depressed.

Warning lamp comes on but no fault Fault code memory which can only be accessed with a PC
codes are flashed on the diagnostic is full.
lamp.

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 Faults that do not generate fault codes

Symptom Cause/Action

The speed limiter is not working. The tachograph is not working.

Engine hesitates temporarily, which The control unit misreads the engine speed and cuts off the
may be put down to misfiring. supply of fuel briefly. The engine never stops when this
happens and no fault code is generated because of the short
time it lasts. The fault has been corrected on control units
manufactured in May, 1997 and later.

Note: Remember that the EDC is basically

a normal mechanical fuel system with added
electronic control. Faults which can arise in
a fuel system without EDC, such as defective
injectors, can also arise in a vehicle with EDC.

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