C18 Marine Generator Set Engines Caterpillar

Use this procedure to troubleshoot any suspect problems with the following sensors:

• Coolant temperature sensor

• Fuel temperature sensor

• Inlet manifold temperature sensor

• Fuel outlet temperature sensor

This procedure covers the following diagnostic codes:

• 110-03 Engine Coolant Temperature open/short to +batt

• 110-04 Engine Coolant Temperature short to ground

• 172-03 Intake Manifold Air Temp open/short to +batt

• 172-04 Intake Manifold Air Temp short to ground

• 174-03 Fuel Temperature open/short to +batt

• 174-04 Fuel Temperature short to ground

• 1929-03 Fuel Return Temperature Sensor high/short to +batt

• 1929-04 Fuel Return Temperature Sensor low/short to ground

The troubleshooting procedures for the diagnostic codes of each temperature sensor are identical. The temperature sensors are passive sensors that have two terminals. The temperature sensors do not require supply voltage from the Electronic Control Module (ECM).

Illustration 1	g01175264
Schematic for engine temperature sensors

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Turn the keyswitch to the OFF position.
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   Illustration 2	g01175267
   Left side engine view (typical engine view) (1) Engine coolant temperature sensor (2) Fuel temperature sensor (3) Fuel outlet temperature sensor (4) Inlet air temperature sensor (5) J2/P2 ECM connector

2. Thoroughly inspect connector (5). Also, thoroughly inspect the connectors for temperature sensors (1), (2), (3), and (4). Refer to Troubleshooting, "Electrical Connectors - Inspect".
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   Illustration 3	g01150540
   P2 terminals that are associated with the engine temperature sensors (P2-18) Sensor return (P2-32) Engine coolant temperature (P2-33) Fuel temperature (P2-34) Fuel outlet (P2-35) Inlet air temperature

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   Illustration 4	g01146837
   Harness connector for the temperature sensors (1) Signal (2) Return

3. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the temperature sensors.

4. Check the allen head screw on each ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.

5. Check the harness and wiring for abrasions and for pinch points from each sensor 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 connectors and wiring appear to be OK. Proceed to Test Step 2.

• Not OK - There is a problem in the connectors and/or wiring.

  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 for Active Diagnostic Codes

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

2. Turn the keyswitch to the ON position.

3. Check for active diagnostic codes on Cat ET. Check and record any active diagnostic codes.

   Note: Wait at least 15 seconds in order for the diagnostic codes to become active.

4. Look for an -03 diagnostic code or an -04 diagnostic code.

Expected Result:

No diagnostic codes are active.

Results:

• OK - No diagnostic codes are active. The problem appears to be resolved.

  Repair: The problem may have been related to a faulty connection in the harness. Carefully reinspect the connectors and wiring. Refer to Troubleshooting, "Electrical Connectors - Inspect" for additional information.

  STOP

• Not OK - An -04 diagnostic code is active at this time. Proceed to Test Step 3.

• Not OK - An -03 diagnostic code is active at this time. Proceed to Test Step 4.

Test Step 3. Disconnect the Suspect Sensor in Order to Create an Open Circuit

1. Turn the keyswitch to the OFF position.

2. Disconnect the suspect sensor from the engine harness.

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

4. Use Cat ET to check for an active -03 diagnostic code for the suspect sensor.

5. Turn the keyswitch to the OFF position.

Expected Result:

An -03 diagnostic code is now active for the suspect sensor.

Results:

• OK - An -04 diagnostic code was active before disconnecting the sensor. An -03 diagnostic code became active after the sensor was disconnected. There may be a problem with the sensor.

  Repair: Temporarily connect a new sensor to the harness, but do not install the new sensor in the engine. Verify that there are no active diagnostic codes for the sensor. If there are no active diagnostic codes for the sensor, permanently install the new sensor. Clear any logged diagnostic codes.

  Verify that the repair eliminates the problem.

  STOP

• Not OK - The -04 diagnostic code is still present. Leave the sensor disconnected. Proceed to Test Step 7.

Test Step 4. Check the Pull-up Voltage at the Sensor Connector

1. Disconnect the suspect sensor at the sensor connector.

2. Turn the keyswitch to the ON position.

3. Measure the voltage between terminal 1 (signal) and terminal 2 (return) at the harness connector.

4. Turn the keyswitch to the OFF position.

Expected Result:

The voltage is 5.5 ± 0.5 VDC.

Results:

• OK - The voltage is 5.5 ± 0.5 VDC. The correct pull-up voltage is present at the harness connector for the suspect sensor.

  Repair: The open circuit is in the sensor or the wire between the sensor and the sensor connector. Replace the sensor. Do not install the sensor in the engine. Verify that no diagnostic codes are active for the suspect sensor before permanently installing the sensor.

  STOP

• Not OK - The voltage is not 5.5 ± 0.5 VDC. Proceed to Test Step 5.

Test Step 5. Check the Signal Wire for a Short Circuit

1. Turn the keyswitch to the OFF position.

2. Disconnect the P1 and P2 connectors.

3. Measure the resistance between the terminal for the suspect sensor's signal wire at the ECM connector and all of the remaining terminals on the P2 connector.

4. Measure the resistance between the terminal for the suspect sensor's signal wire at the ECM connector and all of the terminals on the P1 connector.

5. Measure the resistance between the terminal for the suspect sensor's signal wire at the ECM connector and the engine ground.

6. Connect the J1/P1 and J2/P2 connectors.

Expected Result:

Each check of the resistance indicates an open circuit.

Results:

• OK - Each check of the resistance indicates an open circuit. Proceed to Test Step 6.

• Not OK - At least one check of the resistance does not indicate an open circuit. There is a problem with the wiring. There may be a problem with a connector.

  Repair: Repair the wiring and/or the connectors. Replace parts, if necessary.

  Verify that the original problem is resolved.

  STOP

Test Step 6. Create a Short at the Suspect Sensor Connector

1. Turn the keyswitch to the OFF position.

2. Install a jumper wire between terminals 1 and 2 on the harness connector for the suspect sensor.

3. Turn the keyswitch to the ON position.

4. Wait at least 15 seconds for activation of the -04 diagnostic code.

   Note: Use Cat ET to check for active diagnostic codes before installing the jumper wire and after installing the jumper wire.

5. Remove the jumper wire. Check for an -04 diagnostic code again.

6. Turn the keyswitch to the OFF position.

Expected Result:

An -04 diagnostic code is active when the jumper wire is installed. An -03 diagnostic code is active when the jumper wire is removed.

Results:

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

  Repair: Temporarily connect a new sensor to the harness, but do not install the new sensor in the engine. Verify that there are no active diagnostic codes for the sensor. If there are no active diagnostic codes for the sensor, permanently install the new sensor. Clear any logged diagnostic codes.

  STOP

• Not OK - The -03 diagnostic code remains active with the jumper in place. Proceed to Test Step 7.

Test Step 7. Check the Operation of the ECM

1. Turn the keyswitch to the OFF position.

2. Check the operation of the ECM by creating an open circuit at the ECM:

   1. Disconnect the P2 ECM connector.

   2. Remove the signal wire for the suspect sensor from the P2 connector.

   3. Turn the keyswitch to the ON position. Monitor the "Active Diagnostic Code" screen on Cat ET. Wait at least 15 seconds for activation of the code.

      A -03 diagnostic code should be active for the suspect sensor.

   4. Turn the keyswitch to the OFF position.

3. Check the operation of the ECM by creating a short at the ECM:

   1. Disconnect the P2 ECM connector.

   2. Crimp a terminal onto a jumper wire that is long enough to connect from the ECM connector to engine ground. Install the terminal of the jumper wire into the appropriate terminal location of the ECM connector for the suspect sensor. Ground the other end of the jumper wire.

   3. Connect the P2 connector.

   4. Turn the keyswitch to the ON position.

   5. Monitor the "Active Diagnostic Code" screen on Cat ET. Wait at least 15 seconds for activation of the code.

      An -04 diagnostic code should be active when the wire jumper is installed.

   6. Remove the wire jumper. Return all wiring to the original configuration.

Expected Result:

A -03 diagnostic code is active when the sensor signal wire is removed from the ECM connector. A -04 diagnostic code is active when the signal wire is connected to ground.

Results:

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

  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 or replace the harness.

  If the code is only 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 -03 diagnostic code is not active when the sensor signal wire is disconnected. The -04 diagnostic code is not active when the wire jumper is installed.

  Repair: Replace the ECM. Refer to Troubleshooting, "Replacing the ECM". Verify that the problem is resolved.

  STOP