Barometric Pressure — Data Erratic, Intermittent, or Incorrect Page 1 of 10
FAULT CODE 295
Barometric Pressure — Data Erratic, Intermittent, or
Incorrect
Overview
CODE REASON EFFECT
Fault Code: 295 Barometric Pressure —Data Erratic, Intermittent, or Engine
PID: P108 Incorrect. The ambient air pressure sensor is reading power
SPN: 108 an erratic value at initial key-on. derate
FMI: 2
LAMP: Amber
SRT:
Circuit:
Circuit Description
The barometric pressure sensor is used by the electronic control module (ECM) to monitor
the barometric pressure. This value is one of many inputs used by the ECM to determine
the correct air/fuel ratio for proper engine operation.
Component Location
The barometric pressure sensor is mounted on the main branch of the engine harness near
the ECM. Refer to Procedure 100-002 (Engine Diagrams) in Section E for a detailed
component location view.
Shop Talk
The engine barometric pressure reading is compared to the other pressure sensor values
at initial key-on. If the value of engine barometric pressure does not match the readings
from pressure sensors within a pre-defined tolerance, this fault code is logged. To make the
diagnostic run, turn the keyswitch on for 15 seconds before cranking the engine.
Possible causes of this fault code include:
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z Stuck in-range barometric pressure sensor reading
z High resistance in the barometric pressure sensor signal or return lines.
On-Board Diagnostics (OBD) Information:
z The ECM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs
and fails.
z The ECM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition
cycles that the diagnostic runs and does not fail. The MIL lamp and fault code can
also be cleared using the INSITE™ service tool.
z The fault code will be cleared from memory after 40 consecutive drive cycles where
the diagnostic runs and passes.
Cautions and Warnings
CAUTION
To reduce the possibility of damaging a new ECM, all other active fault
codes must be investigated prior to replacing the ECM.
CAUTION
To reduce the possibility of pin and harness damage, use the following
test leads when taking a measurement:
Part Number 3822758 - male Deutsch/AMP/Metri-Pack test lead
Part Number 3822917 - female Deutsch/AMP/Metri-Pack test lead.
Troubleshooting Steps
STEPS SPECIFICATIONS
STEP 1. Check for sensor circuit fault
codes.
STEP 1A. Check for fault codes. Fault Code 221 or 222 is active?
STEP 2. Check the barometric pressure
sensor and circuit.
STEP 2A. Inspect the barometric Dirty or damaged pins?
pressure sensor and connector
pins.
STEP 2B. Check the circuit Fault Code 222 active?
response.
STEP 2C. Check the circuit Fault Code 221 active?
response.
STEP 3. Check the ECM and engine
harness.
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STEP 3A. Inspect the ECM and Dirty or damaged pins?
engine harness connector pins.
STEP 3B. Check the circuit Fault Code 222 active?
response.
STEP 3C. Check the circuit Fault Code 221 active?
response.
STEP 4. Clear the fault codes.
STEP 4A. Verify the repair INSITE™ reading is within 102 mm Hg
[4 in Hg] of local barometric pressure?
STEP 4B. Clear the fault codes. All fault codes cleared?
Guided Step 1 - Check for sensor circuit fault codes.
Guided Step 1A - Check for fault codes 221 and 222.
Conditions
z Turn keyswitch ON.
z Connect INSITE™ electronic
service tool.
Action
Check for active fault codes.
z Use INSITE™ to read the fault
codes.
Fault Codes 221 or 222 is active? Fault Codes 221 or 222 is active?
YES NO
No Repair No Repair
Appropriate fault code troubleshooting
Go to 2A
tree.
Guided Step 2 - Check the barometric pressure sensor
and circuit.
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Guided Step 2A - Inspect the barometric pressure sensor and connector
pins.
Conditions
z Turn keyswitch OFF.
z Disconnect the barometric
pressure sensor from the engine
harness.
Action
Inspect the engine harness and
barometric pressure sensor connector
pins for the following:
z Corroded pins
z Bent or broken pins
z Pushed back or expanded pins
z Wire insulation damage
z Moisture in or on the connector
z Missing or damaged connector
seals
z Connector shell broken
z Dirt or debris in or on the
connector pins
For general inspection techniques, refer
to Component Connector and Pin
Inspection, Procedure 019-361.
Dirty or damaged pins? Dirty or damaged pins?
YES NO
A defective connection has been detected No Repair
in the sensor or harness connector.
Clean the connector and pins.
Repair the damaged harness, connector,
or pins if possible.
Refer to Procedure 019-071.
Go to 4A Go to 2B
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Guided Step 2B - Check the circuit response.
Conditions
z Turn keyswitch OFF.
z Disconnect the barometric
pressure sensor from the engine
harness.
z Turn keyswitch ON.
z Connect INSITE™ electronic
service tool.
Action
Check for the appropriate ECM
response after 30 seconds.
z Use INSITE™ to read the fault
codes.
Fault code 222 active? Fault code 222 active?
YES NO
No Repair No Repair
Go to 2C Go to 3A
Guided Step 2C - Check the circuit response.
Conditions
z Turn keyswitch OFF.
z Disconnect the barometric
pressure sensor from the
engine harness.
z Turn keyswitch ON.
z Connect INSITE™
electronic service tool.
Action
Place a jumper wire between the
barometric pressure +5 volt
SUPPLY pin and the barometric
pressure SIGNAL pin at the
barometric pressure sensor
connector of the engine harness.
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Refer to the wiring diagram for
connector pin identification.
Check the appropriate circuit
response after 30 seconds.
z Use INSITE™ to read the
fault codes.
Fault Code 221 is active? Fault Code 221 is active?
YES NO
An in-range failure of the No Repair
barometric pressure sensor has
been detected.
Replace the barometric pressure
sensor.
Refer to Procedure 019-014.
Go to 4A Go to 3A
Guided Step 3 - Check the ECM and engine harness.
Guided Step a - Inspect the ECM and engine harness connector pins.
Conditions
z Turn keyswitch OFF.
z Disconnect the engine harness
from the ECM connector.
Action
Inspect the engine harness and ECM
connector pins for the following:
z Corroded pins
z Bent or broken pins
z Pushed back or expanded pins
z Wire insulation damage
z Moisture in or on the connector
z Missing or damaged connector
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Barometric Pressure — Data Erratic, Intermittent, or Incorrect Page 7 of 10
seals
z Connector shell broken
z Dirt or debris in or on the
connector pins
For general inspection techniques, refer
to Component Connector and Pin
Inspection, Procedure 019-361.
Dirty or damaged pins? Dirty or damaged pins?
YES NO
A defective connection has been detected No Repair
in the ECM connector or the engine
harness connector.
Clean the connector and pins.
Repair the damaged harness, connector,
or pins if possible.
Refer to Procedure 019-043.
Go to 4A Go to 3B
Guided Step 3B - Check the circuit response.
Conditions
z Turn keyswitch OFF.
z Disconnect the engine harness
from the ECM.
z Turn keyswitch ON.
z Connect INSITE™ electronic
service tool.
Action
Check for the appropriate circuit
response after 30 seconds.
z Use INSITE™ to read the fault
codes.
Fault Code 222 is active? Fault Code 222 is active?
YES NO
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Barometric Pressure — Data Erratic, Intermittent, or Incorrect Page 8 of 10
No Repair Call for pre-authorization.
Replace the ECM.
Refer to Procedure 019-031.
Go to 3C Go to 4A
Guided Step 3C - Check the circuit response.
Conditions
z Turn
keyswitch
OFF.
z Disconnect
the engine
harness from
the ECM.
z Turn
keyswitch
ON.
z Connect
INSITE™
electronic
service tool.
Action
Place a jumper
wire between the
barometric
pressure +5 volt
SUPPLY pin and
the barometric
pressure SIGNAL
pin at the engine
control module
engine connector.
Check for the
appropriate circuit
response after 30
seconds.
z Use
INSITE™ to
read the fault
codes.
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Fault Code 221 is Fault Code 221 is active?
active?
YES NO
High resistance or a Call for pre-authorization.
short circuit has been
detected in the Replace the ECM.
engine harness.
Refer to Procedure 019-031.
Repair or replace the
engine harness.
Refer to Procedure
019-043.
Go to 4A Go to 4A
Guided Step 4 - Clear the fault code.
Guided Step 4A - Verify the repair.
Conditions
z Connect all components.
z Turn keyswitch ON.
z Connect INSITE™ electronic
service tool.
Action
Start the INSITE Data Monitor/Logger .
z Compare the INSITE™ reading for
Barometric Air Pressure to the
local barometric pressure using the
table below.
Altitude (m) Altitude [ft] Pressure [in-
Hg]
0 (sea level) 0 29.9
915 3000 26.9
1830 6000 24.0
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2744 9000 21.4
3659 12,000 19.0
INSITE™ reading is within 102 mm Hg [4 INSITE™ reading is within 102 mm Hg [4
in Hg] of local barometric pressure? in Hg] of local barometric pressure?
YES NO
No Repair No Repair
Go to 4B Go to 1A
Guided Step 4B - Clear the fault codes.
Conditions
z Connect all components.
z Turn keyswitch ON.
z Connect INSITE™ electronic
service tool.
Action
Clear the fault codes.
z Using INSITE™ electronic service
tool, erase all active and inactive
fault codes.
All fault codes cleared? All fault codes cleared?
YES NO
No Repair No Repair
Repair complete Appropriate troubleshooting steps
Last Modified: 30-Jun-2006
Copyright© 2006
Cummins, Inc.
All rights reserved
12:36:34 2007-07-20
