3126B Marine Engines Caterpillar

Use this procedure to troubleshoot the system only when there is an active diagnostic code or when a diagnostic code can easily be activated. This procedure covers open circuit diagnostic codes and short circuit diagnostic codes that are associated with the following sensors:

• Boost pressure sensor

• Injection actuation pressure sensor

• Engine oil pressure sensor

• Fuel pressure sensor

• Transmission oil pressure sensor

Illustration 1	g01050296

Illustration 2	g01050299
P2 ECM connector

Test Step 1. Check for Active +5 V Sensor Supply Diagnostic Codes

1. Connect the electronic service tool to the service tool connector.

2. Turn the keyswitch to the ON position. Wait at least 15 seconds for activation of the diagnostic codes.

3. Verify that neither of the following diagnostic codes are active:
   • 262-03

   • 262-04

Expected Result:

Neither of the preceding diagnostic codes are active.

Results:

• OK - The diagnostic codes are not active. Proceed to Test Step 2.

• Not OK - At least one of the diagnostic codes is active.

  Repair: Perform the following diagnostic procedure: Troubleshooting, "Analog Sensor Supply Circuit - Test".

  Stop.

Test Step 2. Verify all Active Diagnostic Codes

1. Turn the keyswitch to the ON position. Wait at least 15 seconds for activation of the diagnostic codes.

2. Verify if any of the following diagnostic codes are active:
   • 94-03

   • 94-04

   • 100-03

   • 100-04

   • 102-03

   • 102-04

   • 127-03

   • 127-04

   • 164-03

   • 164-04

Expected Result:

One or more of the preceding diagnostic codes are active.

Results:

• OK - One or more of the preceding diagnostic codes are active. Proceed to Test Step 3.

• Not OK - None of the preceding diagnostic codes are active.

  Repair: If the preceding codes are logged but not active and the engine is not running properly, refer to Troubleshooting, "Troubleshooting without a Diagnostic Code". If the engine is running properly at this time, an intermittent condition may be causing the logged codes. Refer to Troubleshooting, "Electrical Connectors - Inspect".

  Stop.

Test Step 3. Inspect Electrical Connectors and Wiring

1. Thoroughly inspect the J2/P2 connector for the Electronic Control Module (ECM) and the connector for each pressure sensor. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

2. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector and the sensor connectors that are associated with the active diagnostic code.

3. Check the ECM connector (allen head screw) for the proper torque of 6.0 N·m (55 lb in).

4. Check the harness and wiring for abrasions and for pinch points from the sensors back to the ECM.

Expected Result:

All connectors, pins, and sockets are completely coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion, and of pinch points.

Results:

• OK - The harness and wiring are okay. Proceed to Test Step 4.

• Not OK - The harness and/or wiring are damaged.

  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.Clear all logged diagnostic codes.

  Stop.

Test Step 4. Verify that the Diagnostic Code is Still Active

1. Turn the keyswitch to the ON position. Wait at least 15 seconds for activation of the diagnostic codes.

2. Monitor the "Active Diagnostic Code " screen on the electronic service tool. Record any active diagnostic codes.

3. Determine if the problem is related to an open circuit diagnostic code (03) or a short circuit diagnostic code (04).

Expected Result:

Either a short circuit diagnostic code (04) is active or an open circuit diagnostic code (03) is active.

Results:

• SHORT Circuit - A short circuit diagnostic code (04) is active at this time. Proceed to Test Step 5.

• OPEN Circuit - An open circuit diagnostic code (03) is active at this time. Proceed to Test Step 6.

Test Step 5. Disconnect the Sensor in Order to Create an Open Circuit

1. Turn the keyswitch to the OFF/RESET position.

2. Disconnect the sensor connector of the sensor with the short circuit diagnostic code (04).

3. Turn the keyswitch to the ON position. Wait at least 15 seconds for activation of the diagnostic codes.

4. Access the "Active Diagnostic Code" screen on the electronic service tool. Check for an active open circuit diagnostic code (03).

Expected Result:

An open circuit diagnostic code (03) for the disconnected sensor is now active.

Results:

• OK - A short circuit diagnostic code (04) was active before disconnecting the sensor. An open circuit diagnostic code (03) became active after disconnecting the sensor.

  Repair: If the ECM detects the open circuit, the wiring between the sensor and the ECM is okay and the ECM is functioning correctly. Permanently install the new sensor. Clear the logged diagnostic codes.

  Stop.

• Not OK - There is a short circuit between the sensor harness connector and the ECM. Leave the sensor disconnected. Proceed to Test Step 8.

Test Step 6. Measure the Sensor Supply Voltage

Illustration 3	g00810608
Terminals for pressure sensors

1. Turn the keyswitch to the OFF/RESET position.

2. Disconnect the sensor from the engine harness.

3. Turn the keyswitch to the ON position.

4. Measure the voltage from terminal "A" (Analog Sensor Power +5V) to terminal "B" (Analog Sensor Common) on the engine harness side of the connector.

Expected Result:

The voltage between terminal "A" and terminal "B" measures 4.5 to 5.5 VDC.

Results:

• OK - The sensor supply voltage is correct. Proceed to Test Step 7.

• Not OK - The sensor supply voltage is out of the specified range.

  Repair: Perform the diagnostic functional test Troubleshooting, " Analog Sensor Supply Circuit - Test".

  Stop.

Test Step 7. Short the Sensor Connector

1. Turn the keyswitch to the OFF/RESET position.

2. Unplug the suspect sensor.

3. Install a jumper wire with Deutsch sockets on each end between the terminals on the plug for the suspect sensor.

4. Turn the keyswitch to the ON position.

5. Wait at least 15 seconds for activation of the short circuit diagnostic code 04.

   Note: Monitor the "Active Diagnostic Codes" screen on the electronic service tool before installing the jumper wire and after installing the jumper wire.

6. Remove the jumper wire.

7. Turn the keyswitch to the OFF/RESET position.

Expected Result:

A short circuit diagnostic code 04 is active when the jumper wire is installed. An open circuit diagnostic code 03 is active when the jumper wire is removed.

Results:

• OK - The engine harness and the ECM are okay.

  Repair: Perform the following repair:

  1. Temporarily reconnect the suspect sensor.

  2. If the diagnostic code 03 is active, replace the sensor.

  3. Verify that the repair eliminates the problem.

  4. Clear all logged diagnostic codes.

  Stop.

• Not OK - The open circuit diagnostic code 03 remains active with the jumper in place. There appears to be an open circuit between the ECM and the sensor. Proceed to Test Step 8.

Test Step 8. Check the Operation of the ECM by Creating Open and Short Circuits at the ECM Connector

1. Check the operation of the ECM by creating an open at the ECM.

   1. Turn the keyswitch to the OFF/RESET position.

   2. Disconnect the P2 ECM connector. Thoroughly inspect both halves of the connector for signs of corrosion and/or moisture.

   3. Remove the signal wire and the return wire for the suspect sensor from the P2 ECM connector. Reconnect the P2 connector.

      Note: Active open circuit diagnostic codes 03 will be generated for any other temperature sensors that share the return for the suspect sensor.

   4. Turn the keyswitch to the ON position. Monitor the "Active Diagnostic Code" screen on the electronic service tool. Wait at least 15 seconds for activation of the code.

      An open circuit diagnostic code 03 should be active for the suspect sensor. Note the sensor that has the open circuit diagnostic code.

   5. Turn the keyswitch to the OFF/RESET position.

2. Check the operation of the ECM by creating a short at the ECM.

   1. Install a jumper wire with Deutsch sockets on each end between the terminal for the suspect sensor signal and the return for the suspect sensor.

   2. Turn the keyswitch to the ON.

   3. Monitor the "Active Diagnostic Code" screen on the electronic service tool. Wait at least 15 seconds for activation of the code.

      A short circuit diagnostic code 04 should be active for the suspect sensor. Note the sensor that has the short circuit diagnostic code.

   4. Turn the keyswitch to the OFF/RESET position.

   5. Remove the wire jumper and reconnect ECM connector J2/P2.

Expected Result:

An open circuit diagnostic code 03 is active when the sensor wires are removed from the ECM connector. A short circuit diagnostic code 04 is active when the jumper wire is installed across the wires for the sensor.

Results:

• OK - The ECM is working properly. The problem is in the wiring between the ECM and the suspect sensor.

  Repair: If the code is active for more than one sensor, the problem is most likely in the return wire for the sensor. Repair the return wire for the sensor.If the code is active for one sensor, the problem is most likely in the signal wire for the sensor. Repair the signal wire for the sensor.

  Stop.

• Not OK - One of the following conditions exists: The open circuit diagnostic code 03 is not active when the harness is disconnected. The short circuit diagnostic code 04 is not active when the jumper wire is installed.

  Repair: Perform the following repair:

  1. Temporarily connect a spare ECM.

  2. Remove all jumper wires and reconnect all connectors and wires.

  3. Recheck the system for active diagnostic codes.

  4. Repeat this test step.

  5. If the problem is resolved with the spare ECM, reconnect the suspect ECM.

  6. If the problem returns with the suspect ECM, replace the ECM.

  7. Verify that the repair eliminates the problem.

  Stop.