C15 and C18 Petrolem Generator Set Engines Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with a supply circuit or if any one of the diagnostic codes in Table 1 is active or easily repeated.

System Operation

The ECM supplies a regulated voltage of 5.0 ± 0.2 VDC to the following sensors:

• Engine oil pressure sensor

• Fuel pressure sensor

• Intake manifold pressure sensor

• Atmospheric pressure sensor

The supply voltage for the analog sensors is routed from the ECM to terminal 1 of each sensor connector. The analog sensor return for the sensors is routed from the ECM to terminal 2 of each sensor connector. The ECM provides short circuit protection for the internal power supply. A short circuit to the battery will not damage the internal power supply.

If a -10 code is logged, this indicates that the 5 V supply is not available at the sensor connector. During normal engine operation, each of the signals from the pressure sensors fluctuate slightly. When the 5 V supply becomes unavailable at the pressure sensor connector, the signal from that sensor floats to a midrange value. The signal will not fluctuate. If the signal from the sensor remains abnormally steady for more than 30 seconds, the ECM will activate this code.

Note: The sensors are not protected from overvoltage. A short from the supply line to the +Battery may damage the sensors. If any of the -3 diagnostic codes are active, it is possible that a sensor has been damaged. Repair the sensor supply and check for any active sensor diagnostic codes in order to determine if a sensor has failed.

Illustration 1	g01422023
Schematic for the sensor supply circuit

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Remove electrical power from the ECM. Turn the keyswitch to the OFF position.
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   Illustration 2	g01422087
   Sensor locations for the analog sensor supply (1) Intake manifold pressure sensor (2) Fuel pressure sensor (3) Atmospheric pressure sensor (4) Engine oil pressure sensor (5) J2/P2 ECM connectors

2. Thoroughly inspect the connectors for the analog sensors (1 through5).

   Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

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   Illustration 3	g01422088
   P2 ECM connector (P2-15) Intake manifold pressure sensor (P2-17) Analog sensor return (P2-28) Engine oil pressure sensor (P2-40) Fuel pressure sensor (P2-57) Atmospheric pressure sensor (P2-72) Analog sensor supply

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   Illustration 4	g01422120
   Sensor connector (1) Analog sensor supply (2) Analog sensor return (3) Sensor signal

3. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connectors that are associated with the circuit.

4. Check the allen head screw for each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

5. Check the harness and wiring for abrasion and for pinch points from the sensors back to the ECM.

Expected Result:

All connectors, pins, and sockets are 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 are properly in place and ensure that the connectors are coupled.

  Verify that the repair eliminates the problem.

  STOP

Test Step 2. Check for Active Diagnostic Codes

1. Connect Caterpillar Electronic Technician (ET) to the service tool connector.

2. Restore electrical power to the ECM.

3. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes. Look for the following diagnostic codes:

   • 100-10

   • 262-3

   • 262-4

   • 1785-10

   Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

Expected Result:

No diagnostic codes are active.

Results:

• OK - No diagnostic code is active.

  Repair: The problem is no longer present. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - The 100-10 or 1785-10 diagnostic code is logged at this time. The analog sensor supply is not reaching the sensor. Proceed to Test Step 3.

• Not OK - A 262-3 or 262-4 diagnostic code is active at this time. There is a problem with the sensor supply for the analog sensors. Proceed to Test Step 4.

Test Step 3. Check the Supply Voltage at the Sensor Connector

1. Disconnect the harness connectors of the sensor for the diagnostic code.

2. Restore the electrical power to the ECM.

   Note: Be sure to wiggle the harness during the following measurements in order to reveal an intermittent condition.

3. Measure the voltage between terminals 1 and 2 at the connector.

4. Remove the electrical power from the ECM.

5. Connect all of the sensors.

Expected Result:

The voltage measurement is 5.0 ± 0.2 VDC.

Results:

• OK - The voltage measurement is 5.0 ± 0.2 VDC.

  Repair: The analog sensor supply is reaching the sensor connector. There may be a problem with the sensor. Perform the following procedure:

  1. Clear all diagnostic codes.

  2. Run the engine. Allow the engine to warm up. Use Cat ET to check for diagnostic codes that have become active or logged.
  If the code becomes active or logged, the sensor is faulty. Replace the sensor. Verify that the repair eliminates the original problem.

  If the code does not become active or logged, there may be an intermittent problem in the harness or in a connector. If an intermittent problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct troubleshooting procedure.

  STOP

• Not OK - The voltage measurement is not 5.0 ± 0.2 VDC. There is a problem with the harness wiring or with the ECM. Proceed to Test Step 5.

Test Step 4. Disconnect the Analog Sensors while you Monitor the Active Diagnostic Codes

1. Ensure that the ECM is receiving electrical power.

2. Monitor the active diagnostic code screen on Cat ET while you disconnect each 5 V sensor at the sensor connector. Check for an active 262-3 code or an active 262-4 code.

   Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

3. Disconnect the following sensors one at a time:

   • Engine oil pressure sensor

   • Fuel pressure sensor

   • Intake manifold pressure sensor

   • Atmospheric pressure sensor

4. Remove electrical power from the ECM.

Expected Result:

The diagnostic code deactivates when a particular sensor is disconnected.

Results:

• OK - The diagnostic code deactivates when a particular sensor is disconnected.

  Repair: Connect the suspect sensor. If the code returns, replace the sensor. Connect the connectors. Verify that the problem is resolved.

  STOP

• Not OK - The diagnostic code remains active after the sensors are disconnected. Leave the sensors disconnected. The sensors are not the cause of the diagnostic code. Proceed to Test Step 5.

Test Step 5. Check the Analog Supply Voltages at the ECM

1. Disconnect the J2/P2 ECM connector.

2. Fabricate two jumper wires that are long enough to be used to create a test circuit at the ECM connector. Crimp connector sockets to one end of each of the jumper wires.

3. Remove the wires from terminal locations P2-72 (analog sensor supply) and P2-17 (analog sensor return). Install a jumper wire into each of these terminal locations.

4. Connect the J2/P2 ECM connector.

5. Restore electrical power to the engine ECM.

6. Measure the voltage between the jumper wire in P2-72 (analog sensor supply) and the jumper wire in P1-17 (analog sensor return).

7. 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 wire is shorted to another wire in the harness or the supply wire is shorted to engine ground. There may be an open circuit in the supply wire that is in the harness. Repair the supply wire.

  STOP

• Not OK - The voltage measurement is not 5.0 ± 0.2 VDC.

  Repair: The ECM is not generating the correct supply voltage. There is a problem with the ECM. Replace the ECM. Refer to Troubleshooting, "ECM - Replace".

  STOP