Use this procedure to troubleshoot any suspect problems with the +5 V sensor supply.
Use this procedure to troubleshoot the system when one of the following diagnostic codes is active or easily repeated:
- 262-03 5 Volt Sensor DC Power Supply short to +batt
- 262-04 5 Volt Sensor DC Power Supply short to ground
- 100-10 Engine Oil Pressure Sensor abnormal rate of chang
The Electronic Control Module (ECM) supplies a regulated voltage of 5.0 ± 0.2 VDC to the following sensors:
- Atmospheric pressure sensor
- Intake manifold (boost) pressure sensor.
- Engine oil pressure sensor
- Fuel pressure sensor
The supply for the +5 V engine pressure sensor is routed from the ECM to terminal A of each pressure sensor connector. The sensor return from the ECM connector goes to terminal B of each sensor connector. The 5 V sensor supply is output short circuit protected. A short circuit to the battery will not damage the circuit inside the ECM.
Note: The sensors are not protected from overvoltage. A short from the supply line to the +Battery may damage the sensors. If the CID-FMI 262-03 is logged, it is possible that all of the sensors have been damaged. Repair the 5 V sensor supply and check for any active diagnostic codes for the sensor in order to determine if a sensor has failed.
A +5 V diagnostic code is probably caused by a short circuit to ground or a short circuit to another voltage source in the harness. The next likely cause is a problem with a sensor. The least likely cause is a problem with the ECM.
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| Illustration 1 | g01272063 |
Schematic for the pressure sensor supply | |
Test Step 1. Inspect the Electrical Connectors and the Wiring
- Remove electrical power from the ECM.
- Thoroughly inspect connectors (5). Also, thoroughly inspect the connectors for sensors (1), (2), (3), and (4) .
Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect" for details.
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| Illustration 2 | g01142382 |
Typical "C18" sensor locations (1) Intake manifold (boost) pressure sensor (2) Fuel pressure sensor (3) Atmospheric pressure sensor (4) Engine oil pressure sensor (5) J2/P2 ECM connectors (6) J1/P1 ECM connectors | |
- Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector and on each of the wires in the pressure sensor connectors.
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| Illustration 3 | g01024457 |
P2 ECM connector (P2-15) Intake manifold (boost) pressure sensor (P2-17) Sensor return (P2-28) Engine oil pressure sensor (P2-40) Fuel pressure sensor (P2-57) Atmospheric pressure sensor (P2-72) Sensor supply | |
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| Illustration 4 | g01159881 |
Sensor connector (A) Sensor supply (B) Sensor return (C) Sensor signal | |
- Check the allen head screw for each of the ECM connectors and the machine connectors for the proper torque. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
- Check the harness and wiring for abrasions and for pinch points from each of the pressure sensors back to the ECM.
Expected Result:
All 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 OK. Proceed to Test Step 2.
- Not OK - There is a problem with the connectors and/or wiring.
Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals for each of the connectors are properly in place and ensure that the connectors are completely coupled. Verify that the repair eliminates the problem.
STOP
Test Step 2. Check for Active Diagnostic Codes
- Connect Caterpillar Electronic Technician (ET) to the service tool connector.
- Restore electrical power to the ECM.
- Monitor the active diagnostic code screen on Cat ET. Check for an active -03 code, an active -04 code, or an active -10.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
- Remove electrical power from the ECM.
Expected Result:
No diagnostic codes are active.
Results:
- OK - No diagnostic codes are active.
Repair: If any of the above codes are logged and the engine is not running properly, refer to Troubleshooting, "Troubleshooting Without a Diagnostic Code".If the engine is running properly at this time, there may be an intermittent problem in a harness that is causing the codes to be logged. Refer to Troubleshooting, "Electrical Connectors - Inspect".
STOP
- Not OK - There is an active -03 code, an active -04 code, or an active -10 code. Proceed to Test Step 3.
Test Step 3. Disconnect the Pressure Sensors and Check for Active Diagnostic Codes
- Restore electrical power to the ECM.
- Monitor the active diagnostic code screen on Cat ET while you disconnect each pressure sensor connector. Check for an active -03code, an active -04code or an active -10 code.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
- Disconnect the pressure sensors one at a time.
Expected Result:
The diagnostic code deactivates when a particular sensor is disconnected.
Results:
- OK - The -03 code, the -04 code or the -04 diagnostic code deactivates when a particular sensor is disconnected.
Repair: Connect the suspect sensor. If the code returns, replace the sensor. Connect all of the connectors. Verify that the problem is resolved.
STOP
- Not OK - There is an active -03 code, an active -04 code, or an active -10 code after all of the sensors are disconnected. Leave the sensors disconnected. The sensors are not the cause of the diagnostic code. Remove electrical power from the ECM. Proceed to Test Step 4.
Test Step 4. Check the Supply Voltages at the ECM
- Disconnect the J2/P2 ECM connectors.
- Fabricate two jumper wires that are long enough to be used to measure the supply voltage at the ECM connectors. Crimp connector sockets to one end of each jumper wire.
- Remove the wires from terminal locations P2-72 (5 V sensor supply) and P2-17 (sensor return). Install a jumper wire into each of these terminal locations.
- Connect the J2/P2 ECM connectors.
- Restore electrical power to the ECM.
- Measure the voltage between the jumper wire in P2-72 (5 V sensor supply) and the jumper wire in P2-17 (sensor return).
- Remove electrical power from the ECM.
Expected Result:
Each voltage measurement is 5.0 ± 0.2 VDC.
Results:
- OK - The voltage measurement is 5.0 ± 0.2 VDC. The ECM is operating correctly.
Repair: The supply wires are shorted to another wire in the harness or the supply wires are shorted to engine ground. Repair the wiring and/or the connector. Replace parts, if necessary. Verify that the problem is resolved.
STOP
- Not OK - The voltage measurement is not 5.0 ± 0.2 VDC.
Repair: There is a problem with the ECM. Replace the ECM. Refer to Troubleshooting, "Replacing the ECM".
STOP