Table of Contents

MED 9.2.1 Engine Management System

- Workbook
Subject Page

MED 9.2.1
Objectives of the Module........................................................................ 2
Purpose of the System........................................................................... 3
System Components.............................................................................. 4
Principle of Operation............................................................................. 7

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Power Supply
Integrated Voltage Supply Module.......................................................... 8
Local-CAN bus......................................................................................10

Air Management
Auxiliary Air Flaps...................................................................................12
Intake Manifold Pressure Sensors..........................................................12

Fuel Management
Fuel Supply............................................................................................14
High Pressure Injection System.............................................................16
Direct Injection System Control............................................................. 25

Emissions Management
Bosch LSU Planar Wideband Oxygen Sensor.......................................27

Performance Controls
Exhaust Flap......................................................................................... 29
MED 9.2.1 Engine Management System
Model: E66 - 760Li

Production Date: MY 2003

Manufacturer: Bosch

Pin Connector: 134 Pins - 5 Modular Connectors per Control Module

This intent of this workbook is to assist you with diagnosis and testing in addition to the
detailed information found in the the latest Diagnosis and TIS of the DISplus/GT1.

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This section will be instructor led for a brief review of the MED 9.2.1 Engine Management
System. You are encouraged to use this workbook with the latest Diagnosis and TIS infor-
mation to make notes during diagnosis and testing of the new/unique components of the
MED 9.2.1 system. This will be valuable to you as supplementary information or a memo-
ry refresher when performing diagnosis in the future.

Note: For more in depth and detailed information about the MED 9.2.1 Engine Management
System, refer to the ST047 2003 Systems Diagnosis training manual.

For additional and updated information, always refer to:

www.bmwcenternet.com
- Diagnosis and TIS information/updates
- Service Information Bulletins
- DCS messages

Objectives:

After completion of this module you will be able to test and diagnose the following:

• Integrated Voltage Supply Module • High Pressure Injection System

• Local-CAN bus • Direct Injection System Control
• Auxiliary Air Flaps • Bosch LSU Planar Wideband Oxygen Sensor
• Intake Manifold Pressure Sensors • Exhaust Flap

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MED 9.2.1- Workbook
MED 9.2.1

Purpose of the System

The MED 9.2.1 system manages the following functions:

Air: Fuel: Ignition:

• Valvetronic Control • Fuel Supply • Direct Ignition
• Electronic Throttle Valves • HDEV Control • Knock Control
• Hot-Film Air Mass Meters - Fuel Injection • Ignition Monitoring

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MED 9.2.1
ME 9.2 MED 9.2.1
ME 9.2
ECM 1 ECM 2

Emissions: Performance Controls:

• Secondary Air Injection • Bi-VANOS
• Pre and Post Catalyst Oxygen Sensing • Oil Condition
• Oxygen Sensor Heating • Electric Cooling Fan
• Misfire Detection • MAP Thermostat
• Evaporative Purge Control/Leak Testing • Alternator
• Malfunction Indicator Light • E-Box Cooling Fan
• Comfort Start
• Cruise Control
• A/C Compressor (high engine load)
• Exhaust Flap

The basic engine management inputs, processes and outputs are not included in this work-
book because they have not changed, refer to the ST055 Engine Electronics hand out for
details. Some components and functions are the same as the ME 9.2 Engine Management
System found in the E65/E66. Refer to the ST042 E65 Part 2 hand out for details.

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MED 9.2.1- Workbook
System Components
MED 9.2.1 Engine Control Modules - New Features: This Bosch Engine Management
System is introduced for more stringent emission requirements as well as reducing fuel
consumption and increasing driving performance. Flash EEPROMs (additional 1 MB flash
memory) are used as the storage medium for program data, fault code memory as well as
the adaptation values.

The 134 pin MED 9.2.1ECMs are manu- 1

factured by Bosch to BMW specifica-
tions. The ECM is the SKE (standard
shell construction) housing and uses 5
modular connectors.

For testing, use the Universal Adapter

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2
Set (break-out box) Special Tool: # 90 88
6 121 300

The ECMs work in combination with the

Valvetronic Control Module. The N73
engine has a total of 5 control modules 4 5
to manage the engine functions:

1. MED 9.2.1 ECM 2 - overall engine management

3
2. MED 9.2.1 ECM 1 - overall engine management
2
3. Valvetronic Control Module - intake valve lift 1 6

4. High pressure fuel injector control module

(HDEV) - activates injector group for one bank

5. High pressure fuel injector control module

(HDEV) - activates injector group for one bank

These modules are located in the elec-

tronic box in the engine compartment
together with the Integrated Voltage
Supply Module (6).

The ECM controls an electric cooling fan

in the base of the electronic box to draw
in cool air from the passenger compart-
ment.

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MED 9.2.1- Workbook
MED 9.2.1 ECM 1 Inputs - Processing - Outputs

MED 9.2.1
ECM 1

AUXILARY
AIR FLAP ECCENTRIC
SOLENOIDS SENSOR

VALVETRONIC
MOTOR & VALVE
VALVETRONIC RELAY

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HDEV

Fuel Quantity
RAILPRESSURE SENSOR Control Valve

Fuel Shutoff Valve

IGNITION COIL
CONTROL (6x)

EVAP. EMISSION VALVE

IHKA
EXHAUST FLAP
SOLENOID

E-BOX FAN

(2x) AC COMPRESSOR

LOCAL CAN

PT-CAN

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MED 9.2.1- Workbook
MED 9.2.1 ECM 2 Inputs - Processing - Outputs

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MED 9.2.1- Workbook
Principle of Operation

The ME 9.2 Engine Management System from the N62 engine provides the basis for the
MED 9.2.1 Engine Management System.

The main distinguishing features of the MED 9.2.1 are:

• Extended computer capacity (additional 1 MB flash)

• Modified oxygen sensor chip which permits detailed diagnosis of the oxygen sensors
• One MED 9.2.1 control module for each cylinder bank
• Power is supplied to the high pressure fuel injectors for each cylinder bank by a high
pressure fuel injector control module (HDEV)
• Omission of DISA and variable intake manifold activation (N62)
• Three knock sensors for each cylinder bank

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• Activation of the auxiliary air flaps in the air cleaner housing
• Rail pressure sensor
• Fuel quantity control valve

An MED 9.2.1 control module is used for each cylinder bank. Both control modules are
the same design and are classified into ECM 1 and ECM 2 by the programming. ECM 1
receives the input signals from a sensor or switch:

• Accelerator pedal module

• Oil condition sensor
• Alternator
• Coolant temperature
• Oil pressure

ECM 1 transmits these signals via the Local-CAN bus to ECM 2. All further input signals
are transmitted directly to the control module responsible for the relevant cylinder bank (see
overview pages 5 and 6).

Output signals which relate to not just one cylinder bank (e.g. electric fuel pump or exhaust
flap) are transmitted by ECM 1 to the corresponding actuators. The crankshaft sensor sig-
nal is transmitted simultaneously to both control modules.

The MED 9.2.1 regulates the injected fuel quantity. For this purpose, the MED 9.2.1
receives the rail pressure sensor signals and regulates this pressure with the fuel quantity
control valve according to the value defined by the program map. This ensures that a
defined quantity of fuel is injected over the injection period.

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MED 9.2.1- Workbook
Integrated Voltage Supply Module (IVM)
The IVM contains integral relays, replaceable fuses and offers a convenient splice point for
harness connections. The IVM serves as a central power supply for Engine Management
(including Valvetronic), Electronic Transmission and DSC. This diagram is a partial repre-
sentation of the IVM for Engine Electronics.

IVM
Fuse (External)

CAS KL15 Relay 1

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Fuse
Ignition Coils

Relay 5
Fuse (External)
B+KL30 Fuse
Splice
Eng. Mgt. Comp.

Power Module
Fuse (External)

Relay 4

Fuse ECM 2

Fuse (External)
15W (Wake UP)
Relay 3
B+KL30

Local-CAN
KL15 KL50E
Fuse
ECM (1&2)
ECM 1

PT CAN

47-04-04

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MED 9.2.1- Workbook
1. What pin and connector number of ECM 1 and ECM 2 supplies ground to the ECM
(main) relays?
ECM 1 ECM 2

2. What fuse(s) (numbers) supply operating voltage from relay 1 to the ignition coils of:

Cylinder bank 1-6 Cylinder bank 7-12

3. If fuse 005 from relay 3 were defective, what control modules would be affected?

4. Relay 5 supplies operating voltage to what components?

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5. What type of signal is found on pin 26 (X60204) of ECM 2?

Is this signal an input or output?

Where does this signal originate?

What is the voltage value?

Does ECM 1 receive this signal?

6. What type of signal is found on pin 7 (X60201) of ECM 2?

Is this signal an input or output?

Where does this signal originate?

What is the voltage value?

Does ECM 1 receive this signal?

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MED 9.2.1- Workbook
Indirect Signals and Wiring

The ECMs are not directly connected to the OBD diagnostic connector. The OBD diag-
nostic connector is connected to the ZGM. Both ECMs are connected to the ZGM (cen-
tral gateway module) by the PT-CAN bus. ECM 2 is also connected via the Local-CAN bus
to ECM1. The ECMs are also connected to the Valvetronic control module and HDEV con-
trol modules by the Local-CAN bus. Valvetronic faults are stored in the ECMs.

The ECMs are classified into ECM 1 and ECM 2 by the wire harness connections (color
coded) and location. ECM 1 receives the input signals from a sensor or switch and trans-
mits these signals via the Local-CAN bus to ECM 2. All further input signals are transmit-
ted directly (via hardwire harness) to the control module responsible for the relevant cylin-
der bank.

Output signals which are required for both cylinder banks are transmitted by ECM 1 to the

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corresponding actuators. The crankshaft sensor signal is transmitted simultaneously to
both control modules.

KT-9715

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MED 9.2.1- Workbook
PT-CAN

1. What are the circuit descriptions of the three wires that make up the PT-CAN bus?

2. Record the voltage levels on the PT-CAN bus (high and low) using the DISplus scope as
shown - when the bus is:

Inactive - high low Active - high low

Notes on setup:

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47 002

Local-CAN

1. What are the circuit descriptions of the two wires that make up the Local-CAN bus?

2. Record the voltage levels on the Local-CAN bus (high and low) using the DISplus scope
- when the bus is:

Inactive - high low Active - high low

3. What pin and connector numbers did you test the Local-CAN bus circuit on ECM 1?

Pins Connector

4. Are you able to test the Local-CAN bus for resistance? Value:

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MED 9.2.1- Workbook
Air Management

Auxiliary Air Flaps: Each air cleaner housing incorporates an auxiliary air flap in its side
wall. The auxiliary air flaps supply the engine with enough air volume to attain the maximum
performance. The auxiliary air flaps are closed in the lower rpm ranges so that only cooler
ambient air is drawn in for hot idling and stop and go driving.

The auxiliary air flaps are actuated by vacuum diaphragms which are located inside the air
cleaner housings. Both diaphragms are supplied with vacuum from a common solenoid
valve.

The auxiliary air flaps are fully opened by the

ECM:

• In driving position “D” with kickdown

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operation from 3500 rpm

• In driving position “S” from 3000 rpm

and simultaneous full load recognition.

10-15% additional air is drawn in from the engine compartment when the auxiliary air flaps
are open. It is not necessary to draw in additional cold air from outside the engine com-
partment since the engine compartment is adequately ventilated at full load.

Intake Manifold Pressure Sensors: The pressure sensors (one per bank) are located in
the back of intake manifold (1 peizo-electric). The voltage supply from the ECMs is 5 V. The
varying resistance of the sensors is dependent on manifold pressure. The output voltage
signal is processed by the ECMs. The intake manifold pressure is calculated by the ECMs
and is compared with the ambient pressure (internally measured in ECM 1).

A minimum intake manifold vacu-

um of 50 mbar is required for the
fuel tank evaporative purge func-
tion.

This vacuum is set by the elec-

tronic throttle valves (4) and mon-
itoring with the intake manifold
pressure sensors.

Shown to the right is the intake

manifold (upside down) with both
sensors (1). KT-9589

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MED 9.2.1- Workbook
Auxiliary Air Flaps

1. What are the pin and connector numbers at the ECM (1 or 2) for the auxiliary air flap
vacuum solenoid?

2. Is there a Test Plan available for the auxiliary air flaps?

3. Select Control Unit Functions (MED 9.2.1), Diagnosis Requests. Is there a status under
the “Part Functions” column for observing the “Messages and Results”?

Is there a “Component Activation” feature for the auxiliary air flaps?

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Intake Manifold Pressure Sensors

1. What are the pin and connector numbers at the ECM (1 or 2) for the pressure sensors?

Pins Connector

2. Is there a Test Plan available for the pressure sensors?

3. Select Control Unit Functions (MED 9.2.1), Diagnosis Requests. Is there a status under
the “Part Functions” column for observing the “Messages and Results”?

4. What is the value at idle speed? mbar

5. What is the voltage value at pin 2 (X60103) of ECM 1 at:

Idle speed 2000 rpm

6. With the ignition off, unplug the electronic throttle valve (on the bank you are testing).
Restart the engine and check the value at idle speed. mbar

13
MED 9.2.1- Workbook
Fuel Management

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KT-9780
1. Air cleaner 17. Filler vent valve
2. Intake manifold 18. Service vent valve (float valve)
3. Engine 19. Anti-spitback flap
4. Exhaust system 20. Surge chamber (fuel pump baffling)
5. Oxygen sensor 21. Electric fuel pump (EKP)
6. Evaporative emission valve (TEV) 22. Pressure relief valve
7. Purge vapors 23. Suction jet pumps
8. MED 9.2.1 ECM 24. Fuel Tank
9. Carbon Canister 25. Outlet protection valve
10. Fuel tank leak diagnostic module (DM TL) 26. Service vent valve (float valve)
11. Roll-over valve 27. Refueling breather
12. Liquid/vapor expansion tank 28. Leakage line
13. Dust filter 29. Fuel pressure regulator (6 bar)
14. Service ventilation 30. Fuel filter
15. Pressure test lead 31. High pressure fuel pump (HDP)
16. Fuel tank filler cap 32. Fuel rails
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MED 9.2.1- Workbook
Fuel Supply System: For the N73 engine, minor modifications have been made to the fuel
supply system to adapt it to the direct injection system. The additional features are:

• Leakage line
• Electric fuel pump with increased delivery

The N73 in tank electric fuel pump is a roller cell type (EKP Bosch 3.1) with an increased
delivery pressure of 6 bar. This pressure is required to adequately supply the high pressure
fuel pumps.

Fuel Supply System Components:

• Fuel tank (24) • Pressure relief valve (22)

• Surge chamber (20) • Internal tank fuel lines
• Fuel pump (21) • Fuel filter with fuel pressure regulator (30&29)

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• Two suction jet pumps (23) • High pressure fuel pump (HDP)
• Outlet protection valve (25) • Fuel rails with injection valves (32)

Internal Tank Fuel Circuit Operation

The fuel pump supplies fuel from the surge chamber via the fuel filter (located next to the
frame rail under the driver’s floor) to the high pressure fuel pumps (HDP). The fuel pump
always pumps more fuel than the engine requires in all operating conditions. The fuel pres-
sure regulator built into the fuel filter adjusts the pressure to 6 bar and feeds the excess fuel
in the return flow back into the tank.

The pressure regulator valve in the return flow sets a return pressure of 1.0 - 1.5 bar. This
pressure prevents fuel vapor locks in the return flow and also ensures operation of the two
suction jet pumps.

The fuel flows from the pressure regulator valve on to an intersection point where the fuel
return flow is split. Some of the fuel flows through the suction jet pump in the left half of
the tank via the internal fuel line to the surge chamber. The suction jet pump acts like a
venturi tube which draws the fuel from the left half of the tank into the right half.

The other amount of diverted fuel flows via the second internal fuel supply directly to the
right half of the tank and to the second suction jet pump. This pumps the fuel from the right
half of the tank into the surge chamber to ensure that the surge chamber is always filled
with enough fuel in all driving conditions and takes full advantage of the reserve capacity.

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MED 9.2.1- Workbook
High Pressure Injection System: A BMW gasoline direct injection system is used for the
first time in the N73 engine series. Each fuel rail is supplied with fuel by a high pressure
pump (HDP), which is driven via a bucket tappet by a triple lobe cam on the exhaust
camshaft.

The two high pressure pumps are supplied with fuel by the electric fuel pump (EKP), which
is located in the fuel tank. The high pressure fuel injectors are connected to a pressure rail
(accumulator) for each cylinder bank. The two rails are not interconnected.

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KT-9612

1. Supply line 6. High pressure fuel injectors

2. High pressure pumps 7. Rail pressure sensors
3. High pressure lines 8. Pressure limiting valves
4. Fuel rail (7-12) 9. Leakage line
5. Fuel rail (1-6)

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MED 9.2.1- Workbook
High Pressure Pumps: A single cylinder high pressure pump is used for each cylinder
bank. The pumps are mounted on the cylinder heads and driven via bucket tappets by
triple cam lobes on the exhaust camshafts. Each pump has three connecting lines: feed
line, high pressure line and leakage line.

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1. Feed line
2. Inlet valve
3. High pressure chamber
4. Outlet valve
5. High pressure line
6. Pump plunger
7. Annular plunger groove
8. Feed area channel
9. Sealing ring
10. Fuel quantity control
valve
11. Diaphragm
12. Pressure attenuator
13. Mounting flange
14. Leakage line

KT-9698

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MED 9.2.1- Workbook
Fuel is delivered to each high pressure pump through the feed line at a pressure of 6 bar
from the electric in tank fuel pump via a T-branch. In the pump, the fuel passes through
the inlet valve (2) into the high pressure area (3).

As the pump plunger is forced up by the camshaft, the fuel is pressurized (up to 120 bar)
in this area. The pressurized fuel is then forced out through the high pressure line to the
fuel rail. The outlet valve (4) prevents back flow from the rail into the high pressure pump.

Due to the extreme pressure on and around the plunger shaft, a small amount of fuel (max.
1 litre per hour) flows past the plunger shaft against the sealing ring (9). This also serves
as lubrication for the plunger shaft. The sealing ring provides a seal between the fuel side
of the pump and the engine oil at the pump drive.

To relieve the pump pressure (up to 120 bar) at the sealing ring, the pressure is reduced in

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two stages, at which point the fuel returns through the leakage line to the tank. The pump
pressure is reduced down to 6 bar at the annular groove (7) because it is connected by a
channel (8) to the feed area of the pump. The fuel flow from this channel is regulated by
the fuel quantity control valve (MSV).

Below the annular groove, some fuel flows past the pump plunger against the sealing ring.
At this point the fuel pressure is virtually reduced to atmosheric pressure, which is sufficient
to return the fuel through the leakage line to the tank.

Fuel Quantity Control Valves (MSV): The fuel quantity control valve (10) is installed in the
high pressure pump to regulate the fuel delivery rate as required based on load and engine
rpm. This valve opens a channel from the high pressure chamber (3) to the feed area allow-
ing excess fuel to return to the feed area.

When the pump plunger is at it’s lowest position, the valve is energized closed by the ECM.
The valve is de-energized as soon as the injection pressure calculated by the ECM is
reached during the upwards travel of the pump plunger. The valve is now opened to allow
excess fuel to return to the feed area. This switching is repeated three times per camshaft
revolution because the drive cam for the pump has three lobes.

The pulsations generated in the pump during the process are absorbed by the pressure
attenuator spring (12). The pressure attenuator is sealed by a diaphragm (11) from the
pump feed area.

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MED 9.2.1- Workbook
In Tank Electric Fuel Pump

1. Request the Test Plan for the in tank electric fuel pump. What can cause faults in the
fuel supply control?

2. Select #4 “Fault in electric fuel pump”. When the Test Plan requests you to check the
wires and power supply to the fuel pump, can you find a quicker way to confirm this?

3. Is there a “Component activation” for the in tank electric fuel pump?

If yes, how can you confirm that it is operating?

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High Pressure Pump with Fuel Quantity (volume) Control Valve

1. Is there a Test Plan available for the high pressure pump/fuel volume control valve?

2. Select Control Unit Functions (MED 9.2.1), Diagnosis Requests. Is there a status under
the “Part Functions” column for observing the fuel volume control valve?

3. What are the pin and connector numbers at the ECM (1 or 2) for the fuel volume control
valve? Pin Connector

4. Record the voltage value at this pin with the engine not running (ignition on). V
Engine running at idle speed. V

5. Record the frequency at this pin with the engine running at idle speed. Hz
at 2000 rpm. Hz

6. Use the MFK 2 cable to observe a scope pat-

tern from the same pin and record that pat-
tern on the right (engine at idle speed).

Hint: Start out with a scope setting of 10Hz

at 50 V for MFK 2 (Channel B).

Increase the engine speed to 2000 rpm and

observe pattern.

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MED 9.2.1- Workbook
Fuel Rails (pressure accumulator): The fuel
is stored in the fuel rail at a pressure between 50
and 120 bar for distribution to the fuel injectors.
The fuel rail connects to the injectors through
brass coupling connections.

Due to length and position compensation

between the rail and the fuel injectors, brass
coupling connections are used in order that the
DSC00630
fuel injector O-ring can float inside this coupling.

Pressure Limiting Valves: Each fuel rail contains an integral pressure limiting valve (1
below). This valve opens from a pressure of 125 bar to prevent damage to the injection

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system. The outlet of this valve is connected by a line to the high pressure pump fuel feed
line. The valve can open briefly:

• When no fuel is required by the fuel injectors (fuel cutoff when vehicle is coasting)
or
• During the afterheating (hot soak) phase when the hot engine is turned off.

1
2

DSC00632

Rail Pressure Sensors: Each fuel rail incorporates a rail pressure sensor (2 above). The
sensor is a pressure dependent resistor and the voltage (5 V) is supplied by the ECM. The
increasing system pressure alters the sensor resistance.

According to the fuel pressure applied, the rail pressure sensor outputs a varying voltage
signal as the rail pressure increases from 0.5 V (0 bar) to 4.5 V (140 bar). If the rail pres-
sure sensor malfunctions, the fuel quantity control valve (on the HDP) is activated with a
back up function (set value) by the ECM.

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MED 9.2.1- Workbook
Fuel (rail) Pressure Sensor

1. What type of sensor is this?

2. Is there a Test Plan available for the fuel pressure sensor?

3. Select Control Unit Functions (MED 9.2.1), Diagnosis Requests. Is there a status under
the “Part Functions” column for observing the fuel pressure sensor?

4. What are the pin and connector numbers at the ECM (1 or 2) for the fuel pressure sen-
sor? Pin Connector

5. Record the voltage value at this pin with the engine not running (ignition on). V
Engine running at idle speed. V

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Engine speed at 2000 rpm. V

6. Shut the engine off and turn the ignition back on “KL15” (engine not running). Observe
the voltage value at this pin for approximately one minute. What did you observe?

7. If the pressure limiting valve is defective, could the answers to questions 5 and 6 (above)
indicate this?

Additional notes:

21
MED 9.2.1- Workbook
Return Shut-off Valve: The return shut-off valve prevents a pressure drop in the system
while the engine is stopped and is located in the leakage line. When the engine is started,
the valve is energized after a slight delay to prevent a pressure drop in the feed area of the
high pressure pump (cavitation).

While the engine is running, this valve is sup-

plied with system voltage (from the ECM Main
Relay) and activated by the ECM providing a
ground path which allows leakage fuel to return
to the tank.

1. High pressure pump

2. Leakage line
3. Return shut-off valve KT-9618

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Pressure Damper Vent Valve: The Pressure Damper Vent Valve provides a controlled
outlet for fuel/vapors that accumulate in the Pressure Attenuator (damper) chamber in the
top of each High Pressure Pump. This is a 3/2 way electrically controlled valve (KL15 from
the IVM, ground path provided by ECM 1) that provides:

• A circuit for fuel to return to the fuel tank when energized (KL15 on) or
• A circuit for fuel vapors to vent into the evaporative system when de-energized (KL15 off)

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MED 9.2.1- Workbook
When the engine is running, a slight amount of fuel may accumulate in the Pressure
Attenuator upper chambers due to natural leakage through the internal diaphram (extreme
pressure). This fuel (circuit) is returned to the fuel tank by combining with the Leakage Line
of the Return Shut-off Valve. The Pressure Damper Vent Valve provides a passage to com-
bine these two circuits when the ignition is switched on (KL15) and isolates the Evaporative
Emission circuit.

When the engine is not running, fuel vapors remain in these chambers and is routed into
the Evaporative Emission circuit. This is accomplished by Pressure Damper Vent Valve
blocking the passage from the Return Shut-off Valve (KL15 off) and opening a passage to
the circuit leading from the Active Charcoal Canister to the Evaporative Emission Valve.

High Pressure Fuel Injectors (HDEV): The high pressure fuel injectors are designed

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essentially the same as conventional fuel injectors. They are secured by a taper in the cylin-
der head and sealed by a Teflon ring against the combustion chamber.

The O-ring seals the top of the injector and floats inside the brass coupling connections on
the fuel rail. Each fuel injector incorporates a single hole nozzle with a spray angle of 70º
to the piston crown.

1. Electrical connection
2. Solenoid coil
3. Fuel inlet port
4. Pressure spring
5. Nozzle needle
6. Single hole nozzle

KT-9744

To open the high pressure fuel injector, the nozzle needle is lifted off its seat when the sole-
noid coil is energized. Due to the high injection pressure (up to 120 bar), the pressure
spring is designed to accommodate a pressure force of 30 newtons (5 newtons for con-
ventional fuel injectors). The pressure spring forces the nozzle needle onto its seat during
closing with sufficient contact pressure.

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MED 9.2.1- Workbook
Return (flow) Shut-off Valve

1. Is there a Test Plan available for the return flow shut off valve?

2. Select Control Unit Functions (MED 9.2.1), Diagnosis Requests. Is there a status under
the “Part Functions” column for observing the return flow shut off valve?

3. What are the pin and connector numbers at the ECM (1 or 2) for the return flow shut off
valve? Pin Connector

4. Measure and record the resistance value of this valve. ohms

5. Record the voltage value at this pin with the engine not running (ignition on). V

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Engine running at idle speed. V
Engine speed at 2000 rpm. V

6. Shut the engine off. Wait ten seconds and restart the engine. Observe the voltage value
at this pin while the engine cranks and starts. What did you observe?

High Pressure Fuel Injectors (HDEV)

1. What is the resistance value of a high pressure fuel injector? ohms

Visual identification of the high pressure fuel injector:

1. Teflon ring (combustion chamber seal)

2. Taper (seats against cylinder head)
3. O-ring (brass coupling seal in fuel rail)

KT-9637
Additional notes:

24
MED 9.2.1- Workbook
Direct Injection System Control

A high pressure fuel injector control module (HDEV) is used for each cylinder bank and is
located in the engine compartment E box. The HDEV control module is supplied with sys-
tem voltage from the ECM main relay (in the IVM). Data is transmitted from the ECMs to
the HDEV control modules for each high pressure fuel injector via the Local-Can bus. The
HDEVs activate the injectors individually.

Note: The high pressure fuel injectors are activated by the HDEV control modules with a
voltage of 100 V and energized during the opening period with approx. 85 V.

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Partial circuit of ECM (DME) 1
with two injectors shown

HDEV Control Modules: The HDEV control modules contain pulse width modulated final
output stages with high performance capacitors to transform the system voltage up to 85
to 100 volts. Current flows in the output stages up to a specific cutoff value. This cutoff
creates an induced voltage, e.g. 85 V, which is then charged to the high performance
capacitors (boosters). The high pressure fuel injectors are actuated by this capacitor with
2.8 to 16 amps of current.

25
MED 9.2.1- Workbook
High Pressure Fuel Injector Control Module (HDEV)

1. Is there a Test Plan available for the HDEV?

2. Select Control Unit Functions (MED 9.2.1), Diagnosis Requests. Is there a status under
the “Part Functions” column for observing the HDEV injector output?

3. What are the pin and connector numbers at the ECM (1 or 2) for the fuel injector output
request? Connector Pins

4. Record the voltage value at one of these pins with:

The engine not running (ignition on). V

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Engine running at idle speed. V
Rev engine up to 2000 rpm. V

5. What are the pin and connector numbers at the HDEV (1 or 2) for the output control of
one of the fuel injectors? Connector Pins
voltage ground
Ask the Instructor for assistance:
6. Using the ground pin of this fuel injector at the HDEV, record the voltage value with:
The engine not running (ignition on). V
Engine running at idle speed. V
Rev engine up to 2000 rpm. V

7. Use the MFK 2 cable to observe a scope

pat-
tern from the same pin and record that pat-
tern on the right (engine at idle speed).

Hint: Start out with a scope setting of 10Hz

at 100 V for MFK 2 (Channel B).

Increase the engine speed to 2000 rpm and

observe pattern.

HDEV activation (sample shown to the right):

1. Premagnetization time
2. Booster phase
3. Starting current phase
4. Holding current phase

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MED 9.2.1- Workbook
Emissions Management - N73B60 Low Emission Vehicle (LEV)

Oxygen Sensors: The N73 engine is fitted with a total of four oxygen sensors. One pla-
nar broadband oxygen sensor (constant characteristic curve), which regulates the fuel-air
mixture, is located upstream of each of the two catalytic converters. The catalytic converter
assemblies are integral with the exhaust manifolds.

There is a post catalytic converter sensor

(Bosch LSH25) for each cylinder bank posi-
tioned downstream of the catalytic converter
which monitors the catalyst efficiency.

This monitoring means that if the exhaust gas

concentration is too high, a fault code is

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stored. The post catalyst sensors can also
detect an emission relevant fault in a pre-cat-
alyst oxygen sensor. N73 Oxygen Sensors

Bosch LSU Planar Wideband Oxygen Sensor: The N73 engine is equipped with planar
wideband oxygen sensors (pre-catalyst). The sensor is planar shaped (type of construc-
tion) which is more compact and is made up of thin layers of zirconium dioxide (ZrO2)
ceramic films. This modular lamination structure enables the integration of several functions
including the heating element which ensures the minimum operating temperature (750 ºC)
is reached rapidly.

In contrast to conventional oxygen sensors, the wideband features can measure not only
at Lambda=1, but also in the rich and extremely lean range (Lambda=0.7 to complete
atmospheric oxygen) very rapidly.

The pump cell and reference cell are made of zirconium dioxide and each coated with two
porous platinum electrodes. They are arranged so that there is a measuring gap between
them. This measuring gap is connected by an inlet opening to the exhaust gas. The pump
cell is controlled by the ECMs applying voltage to the electrodes to initiate oxygen ion
pumping across the porous membrane of the reference cell, providing a quicker response
time.

The pump current flow is proportional to the oxygen concentration (lean) or the oxygen
requirement (rich). The pump is constantly working to maintain that the gas composition in
the measuring gap is constantly at Lambda=1.

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MED 9.2.1- Workbook
Bosch LSU Planar Wideband Oxygen Sensor

1. Is there a Test Plan available for the LSU oxygen sensor?

2. Select Control Unit Functions (MED 9.2.1), Diagnosis Requests. Is there a status under
the “Part Functions” column for observing the LSU oxygen sensor?

List the status that apply to the oxygen sensor:

3. Using the DISplus voltmeter, connect MFK2 to the full circuit of the oxygen sensor.
(for example: pin 13 to pin 20 at ECM 1 of LSU bank 1). Start engine and allow warmup.

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Select Control Unit Functions (MED 9.2.1), Diagnosis Requests. Under the “Part
Functions” column for the LSU oxygen sensor, select: Oxygen-sensor control, Oxygen-
sensor controller, Lambda value, Additive lambda adaptation and Multiplicative lambda
adaptation - now select “Display”.

Ask the Instructor for assistance:

4. With the engine running and the voltmeter displayed, introduce a vacuum leak.

With the Minimum/Maximum feature selected, observe the voltage value and reconnect
the hose.
What is the minimum? V maximum? V

5. Slowly disconnect the hose and allow the engine to run for approximately 1 - 2 minutes.
Under the “Part Functions” column for the LSU oxygen sensor, record the values for:

Oxygen-sensor control Additive lambda adaptation

Oxygen-sensor controller Multiplicative lambda adaptation
Lambda value

Caution: Do not conduct this test for longer than 5 minutes! (allow engine to cool)

6. What do the values from question 5 indicate?

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MED 9.2.1- Workbook
Performance Controls

Exhaust Flap: The 12.6 liter rear silencer (4) is fitted with an exhaust flap to keep noise to
a minimum at engine idle speed and low rpm. The flap provides exhaust efficiency based
on two effects:

• Minimization of the cross section (slight back pressure) and the outlet noise level at low
exhaust flow rates

• Large cross-section with low backpressure at high speeds and loads

The exhaust flap is opened allowing additional flow when:

• The transmission gear is engaged and

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• The engine speed is approximately above 1,500 rpm

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A vacuum controlled diaphragm (2 - actuator mounted on the silencer) opens and closes
the exhaust gas flap. The vacuum is supplied from the camshaft driven vacuum pump.

The exhaust flap is opened with vacuum, and is sprung closed by the actuator (when vac-
uum is not present). The procedure is carried out using a solenoid valve (1) which is elec-
trically controlled by the ECM and located in the left rear luggage compartment (below the
light assembly).

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MED 9.2.1- Workbook
Exhaust Flap

1. Select Control Unit Functions (MED 9.2.1), Diagnosis Requests. Is there a status under
the “Part Functions” column for observing the “Messages and Results”?

Is there a “Component Activation” feature for the exhaust flap?

2. Is there a Test Plan available for the exhaust flap?

3. If so, does the engine need to be run? Why?

4. What are the pin and connector numbers at the ECM for the exhaust flap solenoid acti-
vation?

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Pin Connector

5. Which ECM controls the exhaust flap (1 or 2)?

Additional notes:

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MED 9.2.1- Workbook