3508C, 3512C, and 3516C Locomotive Engines Caterpillar

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

System Operation

The Electronic Control Module (ECM) supplies a regulated voltage of 5.0 ± 0.5 VDC to the following sensors:

• Aftercooler temperature sensor

• Atmospheric pressure sensor

• Coolant temperature sensor

• Crankcase pressure sensor

• Filtered engine oil pressure sensor

• Filtered fuel pressure sensor

• Left turbocharger inlet pressure sensor

• Right turbocharger inlet pressure sensor

• Turbocharger outlet pressure sensor

• Unfiltered engine oil pressure sensor

• Unfiltered fuel pressure sensor

The ECM supplies a regulated voltage of 8.0 ± 0.4 VDC to the following sensors:

• Left exhaust temperature sensor

• Right exhaust temperature sensor

The supply voltage for the sensors is routed from the ECM to terminal A of each sensor connector. The sensor return for the sensors is routed from the ECM to terminal B 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.

Note: The sensors are not protected from overvoltage. A short from the supply line to the +Battery may damage the sensors. If the diagnostic code 262-3 or the diagnostic code 263-3 is logged, it is possible that all of the sensors have 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	g01257792
Typical schematic of 5 V supply

Illustration 2	g01212477
Typical schematic of 8 V supply

Illustration 3	g01212479
P1 ECM connector (P1-2) 5 V sensor supply (P1-3) Sensor return (P1-4) 8 V supply (P1-5) Digital return (P1-6) Aftercooler temperature sensor (P1-7) Coolant temperature sensor (P1-11) Left exhaust temperature sensor (P1-12) Right exhaust temperature sensor (P1-16) Filtered engine oil pressure sensor (P1-17) Unfiltered engine oil pressure sensor (P1-24) Filtered fuel pressure sensor (P1-25) Unfiltered fuel pressure sensor

Illustration 4	g01212480
P2 ECM connector (P2-36) Turbocharger outlet pressure sensor (P2-37) Atmospheric pressure sensor (P2-38) Left turbocharger inlet pressure sensor (P2-39) Right turbocharger inlet pressure sensor (P2-46) Crankcase pressure sensor

Illustration 5	g01094844
Sensor connector (Pin A) Sensor supply (Pin B) Sensor return (Pin C) Signal

Illustration 6	g01234146
Location of ECM connectors

Test Step 1. Inspect Electrical Connectors and Wiring

1. Turn the main disconnect switch to the OFF position.

2. Thoroughly inspect the J1/P1 ECM connector and the J2/P2 ECM connector. Inspect all of the connectors that are associated with the circuit.

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

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 ECM connector (allen head screw) 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 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 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

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

2. Turn the main disconnect switch to the ON position.

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

   • 262-3

   • 262-4

   • 263-3

   • 263-4

   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 - Either the 262-3 or 262-4 diagnostic code is active at this time. Proceed to Test Step 3.

• Not OK - Either the 263-3 or 263-4 diagnostic code is active at this time. Proceed to Test Step 5.

Test Step 3. Disconnect the 5 Volt Sensors while you Monitor the Active Diagnostic Codes

1. Monitor the active diagnostic code screen on Cat ET while you disconnect each 5 Volt sensor at the sensor connector. If the problem is in a sensor, the active 262-3 code or the active 262-4 code will deactivate when you disconnect the sensor.

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

   1. Disconnect the following sensors one at a time:

      • Aftercooler temperature sensor

      • Atmospheric pressure sensor

      • Coolant temperature sensor

      • Crankcase pressure sensor

      • Filtered engine oil pressure sensor

      • Filtered fuel pressure sensor

      • Left turbocharger inlet pressure sensor

      • Right turbocharger inlet pressure sensor

      • Turbocharger outlet pressure sensor

      • Unfiltered engine oil pressure sensor

      • Unfiltered fuel pressure sensor

Expected Result:

The diagnostic code deactivates when a particular sensor is disconnected.

Results:

• OK - The 262-3 or 262-4 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 - The 262-3 or 262-4 diagnostic code remains active after all of the sensors are disconnected. Leave the sensors disconnected. The sensors are not the cause of the diagnostic code. Proceed to Test Step 4.

Test Step 4. Check the 5 Volt Supply Voltages at the ECM

1. Turn the main disconnect switch to the OFF position.

2. Disconnect the J1/P1 ECM connector.

3. Remove the supply wire(s) from the appropriate ECM connector. Install a wire jumper(s) into the socket(s) for the sensor supply.

4. Turn the main disconnect switch to the ON position.

5. Measure the voltage between the wire jumper(s) and the analog return.

6. Turn the main disconnect switch to the OFF position.

7. Remove the wire jumpers and replace all wires.

Expected Result:

Each voltage measurement is 5.0 ± 0.5 VDC.

Results:

• OK - The voltage measurement is 5.0 ± 0.5 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. Repair the supply wire.

  STOP

• Not OK - The voltage measurement is not 5.0 ± 0.5 VDC.

  Repair: Replace the ECM. Refer to Troubleshooting, "ECM - Replace".

  STOP

Test Step 5. Disconnect the 8 Volt Sensors while you Monitor the Active Diagnostic Codes

1. Monitor the active diagnostic code screen on Cat ET while you disconnect each 8 Volt sensor at the sensor connector. If the problem is in a sensor, the active 263-3 code or the active 263-4 code will deactivate when you disconnect the sensor.

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

   1. Disconnect the following sensors one at a time:

      • Left exhaust temperature sensor

      • Right exhaust temperature sensor

Expected Result:

The diagnostic code deactivates when a particular sensor is disconnected.

Results:

• OK - The 263-3 or 263-4 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 - The 263-3 or 263-4 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 6.

Test Step 6. Check the 8 Volt Supply Voltage at the ECM

1. Turn the main disconnect switch to the OFF position.

2. Remove the supply wire from P1-4. Install a wire jumper into the socket for P1-4.

3. Remove the supply wire from P2-56. Install a wire jumper into the socket for P2-56.

4. Turn the main disconnect switch to the ON position.

5. Measure the voltage between the wire jumper in terminal P1-4 and engine ground.

6. Measure the voltage between the wire jumper in terminal P2-56 and engine ground.

7. Turn the main disconnect switch to the OFF position.

8. Remove the wire jumper and reconnect all wires. Reconnect ECM connector J1/P1.

Expected Result:

The voltage measurement is 8.0 ± 0.4 VDC.

Results:

• OK - The voltage measurement is 8.0 ± 0.4 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. Repair the supply wire.

  STOP

• Not OK - The voltage measurement is not 8.0 ± 0.4 VDC.

  Repair: Replace the ECM. Refer to Troubleshooting, "ECM - Replace".

  STOP