Use this procedure to troubleshoot any suspect problems with the following sensors:
- Atmospheric pressure
- Auxiliary pressure
- Coolant temperature
- Engine oil pressure
- Engine oil temperature
- Fuel temperature
- Fuel pressure
- Injection actuation pressure
- Inlet air temperature
- Turbocharger outlet pressure
This procedure covers the following diagnostic codes:
- 094-03 Fuel Pressure open/short to +batt
- 094-04 Fuel Pressure short to ground
- 100-03 Engine Oil Pressure open/short to +batt
- 100-04 Engine Oil Pressure short to ground
- 105-03 Inlet Manifold Temp Sensor open/short to +batt
- 105-04 Inlet Manifold Temp Sensor short to ground
- 110-03 Engine Coolant Temperature open/short to +batt
- 110-04 Engine Coolant Temperature short to ground
- 164-03 Injector Actuation Pressure voltage high
- 164-04 Injector Actuation Pressure voltage low
- 174-03 Fuel Temperature open/short to +batt
- 174-04 Fuel Temperature short to ground
- 175-03 Engine Oil Temperature open/short to +batt
- 175-04 Engine Oil Temperature short to ground
- 273-03 Turbo Outlet Pressure open/short to +batt
- 273-04 Turbo Outlet Pressure short to ground
- 274-03 Atmospheric Pressure open/short to +batt
- 274-04 Atmospheric Pressure short to ground
- 1835-03 Auxiliary Pressure Sensor open/short to +batt
- 1835-04 Auxiliary Pressure Sensor short to ground
The ECM performs an automatic calibration of the pressure sensors when the ECM is powered after a five second shutdown. During an automatic calibration, the ECM calibrates pressure sensors against the atmospheric pressure sensor and an acceptable offset pressure range.
Note: Refer to Troubleshooting, "Analog Sensor Supply Circuit - Test" if the ECM has detected a problem with the analog sensor supply voltage.
Note: There are separate procedures for troubleshooting opens and/or shorts in digital engine sensor circuits. Refer to the appropriate topic in the "Troubleshooting with a Diagnostic Code" section of this manual.
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| Illustration 1 | g01058417 |
Schematic | |
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The connection of any electrical equipment and the disconnection of any electrical equipment may cause an explosion hazard which may result in injury or death. Do not connect any electrical equipment or disconnect any electrical equipment in an explosive atmosphere. |
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Test Step 1. Inspect the Electrical Connectors and the Wiring
- Turn the keyswitch to the OFF position.
- Thoroughly inspect connectors (4), (5), and (7). Also inspect the connector for each engine pressure sensor and for each engine temperature sensor. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
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| Illustration 2 | g01135982 |
(1) Coolant temperature sensor (2) Turbocharger outlet pressure sensor (3) ECM (4) J1/P1 ECM connector (5) J2/P2 ECM connector (6) Injection actuation pressure sensor (7) J3 Customer connector (8) Fuel presssure sensor connector (9) Primary engine speed/timing sensor (10) Secondary engine speed/timing sensor (11) Fuel temperature sensor (12) Atmospheric pressure sensor (13) Engine oil pressure sensor (14) Engine oil temperature sensor (15) Injection actuation pressure control valve (IAPCV) | |
- Perform a 45 N (10 lb) pull test on each of the wires for each sensor on the engine.
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| Illustration 3 | g01136865 |
P1 Terminals for the engine sensors (P1-17) Auxiliary pressure sensor (P1-30) Analog sensor return (P1-31) Engine oil temperature sensor (P1-36) Analog sensor supply (P1-37) Injection actuation pressure sensor | |
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| Illustration 4 | g01136867 |
P2 terminals for the engine sensors (P2-2) Fuel pressure sensor (P2-8) Engine oil pressure sensor (P2-9) Coolant temperature sensor (P2-14) Inlet air temperature sensor (P2-15) Fuel temperature sensor (P2-20) Atmospheric pressure sensor (P2-23) Turbocharger outlet pressure sensor | |
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| Illustration 5 | g01136869 |
P3 terminals for the engine sensors (14) Analog sensor supply (15) Analog sensor return (20) Fuel pressure sensor (33) Auxiliary pressure sensor | |
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| Illustration 6 | g01123211 |
Connectors for the sensors (A) Analog sensor supply (B) Analog return (C) Signal | |
- Check the torque of the allen head screw on the ECM connectors and the customer connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
- Check the harness and the wiring for abrasion and for pinch points from each sensor back to the ECM.
Expected Result:
All of the connectors, pins and sockets are completely coupled and/or inserted and the harness and wiring are free of corrosion, of abrasion and of pinch points.
Results:
- OK - The harness and connectors appear to be in good repair. Proceed to Test Step 2.
- Not OK - The connectors and/or wiring need repair.
Repair: Repair the wiring and/or the connectors. Replace parts, if necessary. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled. Verify that the repair eliminates the problem.
STOP
Test Step 2. Check the Sensor Supply Voltage at the Sensor Connector
- Disconnect the suspect sensor.
- Turn the keyswitch to the ON position.
- Use a multimeter to measure the voltage across terminal A (analog sensor supply) and terminal B (analog return) at the harness side of the suspect sensor connector.
- Turn the keyswitch to the OFF position.
Expected Result:
The analog sensor supply voltage is 5.0 ± 0.5 VDC.
Results:
- OK - The supply voltage is reaching the sensor. Proceed to Test Step 3.
- Not OK - The supply voltage is not reaching the sensor.
Repair: Refer to Troubleshooting, "Analog Sensor Supply Circuit - Test" for the appropriate troubleshooting procedure.
STOP
Test Step 3. Short the Sensor Signal at the Sensor Connector
- Connect Caterpillar Electronic Technician (ET) to the service tool connector.
- Disconnect the suspect sensor from the harness.
- Turn the keyswitch to the ON position.
- Check for active diagnostic codes on Cat ET.
- Use a jumper wire to short terminal B (analog return) and terminal C (signal) at the harness side of the suspect sensor connector.
- Check the active diagnostic codes on Cat ET.
Expected Result:
The FMI for the active diagnostic code changes from a "-03" (open/short to +Battery) to a "-04" (short to ground) when the terminals are shorted.
Results:
- OK - The harness appears to be OK. The problem is with the sensor.
Repair: Replace the suspect sensor. Verify that the repair eliminates the problem.
STOP
- Not OK - Proceed to Test Step 4.
Test Step 4. Measure the Resistance of the Signal Wire
- Turn the keyswitch to the OFF position.
- Disconnect the suspect sensor and the appropriate ECM connector for that sensor.
- Measure the resistance between terminal C (signal) at the harness side of the suspect sensor connector and the appropriate terminal for the sensor signal at the ECM connector.
Expected Result:
The resistance through the signal wire is less than 10 Ohms.
Results:
- OK - The sensor signal wire does not have an open circuit. Proceed to Test Step 5.
- Not OK - There is an open circuit or excessive resistance in the signal circuit of the harness.
Repair: Repair the wire and/or the connector, when possible. Replace parts, if necessary. Verify that the problem is resolved.
STOP
Test Step 5. Short the Sensor Signal at the ECM
- Turn the keyswitch to the OFF position.
- Install a 40-pin breakout at the ECM connector for the suspect sensor.
- Remove the signal wire for the suspect sensor from the appropriate ECM connector.
- Turn the keyswitch to the ON position.
- Check the active diagnostic codes on Cat ET.
- Use a jumper wire to short the terminal for the suspect sensor signal to P1-30 (analog return) at the breakout.
- Check the active diagnostic codes on Cat ET.
Expected Result:
The FMI for the active diagnostic code changes from a "-03" (open/short to +Battery) to a "-04" (short to ground) when the terminals are shorted.
Results:
- OK - There is a problem in the wiring between the suspect sensor and the ECM.
Repair: Repair the wire and/or the connector, when possible. Replace parts, if necessary. Verify that the problem is resolved.
STOP
- Not OK - The ECM is not reading the sensor circuit.
Repair: Replace the ECM. Refer to Troubleshooting, "Replacing the ECM" before you replace the ECM. Verify that the repair eliminates the problem.
STOP