G3516C, G3516E, and G3512E Generator Set Engines Caterpillar

Use this procedure to troubleshoot diagnostic codes for open circuits or short circuits for the engine coolant temperature sensor.

This procedure covers the following diagnostic codes:

• 110-3 Engine Coolant Temperature Sensor : Voltage Above Normal

• 110-4 Engine Coolant Temperature Sensor : Voltage Below Normal

The engine coolant temperature sensor does not require +5 VDC from the Electronic Control Module (ECM). The engine coolant temperature sensor is a passive sensor of the analog type. The sensor operates without a voltage supply from the ECM.

A -3 code is probably caused by a problem in an engine harness. There may be an open circuit in a harness, or a short circuit to a positive voltage source in a harness. The next likely cause is a sensor problem. The least likely cause is a problem with the ECM.

An -4 code is probably caused by a short circuit to ground in an engine harness. The next likely cause is a sensor problem. The least likely cause is a problem with the ECM.

Logged diagnostic codes provide a historical record. Before you begin this procedure, use Caterpillar Electronic Technician (ET) to print the logged codes to a file.

This troubleshooting procedure may generate additional diagnostic codes. Keep your mind on correcting the cause of the original diagnostic code. Clear the diagnostic code after the problem is resolved.

Illustration 1	g01325355
Schematic for the analog sensor

Test Step 1. Inspect the Electrical Connectors and Wiring

1. Remove the electrical power from the engine.

   Note: For the following steps, refer to Troubleshooting, "Electrical Connectors - Inspect".

2. Thoroughly inspect each of the following connectors:

   • J1/P1 connectors

   • J7/P7 connectors

   1. Check the torque of the allen head screws for the ECM connectors.

   2. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the analog sensors.

   3. Check the harness and wiring for abrasion and for pinch points from the analog sensors to the ECM.

Expected Result:

All connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points.

Results:

• OK - All connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points. The components are in good condition with proper connections. If you are troubleshooting a -3 code, proceed to Test Step 3. If you are troubleshooting a -4 code, proceed to Test Step 2.

• Not OK - At least one of the connectors, pins, and/or sockets are not connected properly. At least one of the connectors and/or the wiring has corrosion, abrasion, or pinch points.

  Repair: Perform the necessary repairs and/or replace parts, if necessary.

  STOP

Test Step 2. Create an Open Circuit for the Sensor

1. Disconnect the sensor that has the "voltage below normal" diagnostic code.

2. Observe the "Active Diagnostic" screen on Cat ET. Allow a minimum of 30 seconds for any codes to activate. Look for an active -3 diagnostic code.

Expected Result:

There is an active -3 diagnostic code for the disconnected sensor.

Results:

• Yes - Before the suspect sensor was disconnected, there was an active -4 diagnostic code for the sensor. After the suspect sensor was disconnected, there was an active -3 diagnostic code for the sensor.

  Repair: Reconnect the sensor. If the active -4 diagnostic code recurs, replace the original sensor.

  Verify that the code does not activate when the new sensor is installed. Clear the logged codes from the ECM.

  STOP

• No - Before the suspect sensor was disconnected, there was an active -4 diagnostic code for the sensor. After the suspect sensor was disconnected, the active -4 diagnostic code remained. Proceed to Test Step 3.

Test Step 3. Check the Pull-Up Voltage at the Sensor

1. Verify that the suspect sensor's connector is disconnected from the engine harness.
   Show/hide table

   Illustration 2	g01303636
   Harness connectors for the sensor (1) Signal (2) Return

2. At the harness connector for the suspect sensor, measure the voltage between terminals (1) and (2).

Expected Result:

The voltage is between 6.0 VDC and 7.0 VDC.

Results:

• OK - The voltage between the signal terminal and the return terminal is between 6.0 VDC and 7.0 VDC. The pull-up voltage that is created by the ECM is present at the sensor connector. The signal wire and the return wire for the suspect sensor appear to be OK. Proceed to Test Step 5.

• Not OK - The voltage between the signal terminal and the return terminal is not between 6.0 VDC and 7.0 VDC. The pull-up voltage that is created by the ECM is not present at the sensor connector. Proceed to Test Step 4.

Test Step 4. Check the Pull-Up Voltage at the ECM

1. Use a 151-6320 Wire Removal Tool to remove the signal wire for the suspect sensor from the P1 connector.

2. Use a jumper wire with Deutsch terminals on the ends. Insert one end of the jumper wire into the open terminal of the P1 connector.

3. Connect a multimeter lead to the end of the jumper wire that is not inserted into the connector.

4. At the harness side of the P1 connector, insert a 7X-1710 Multimeter Probe along terminal 3.

5. Connect the other multimeter lead to the probe.

6. Measure the pull-up voltage at the ECM.

Expected Result:

The voltage is between 6.0 VDC and 7.0 VDC.

Results:

• OK - The pull-up voltage for the suspect sensor at the ECM is between 6.0 VDC and 7.0 VDC. The ECM is producing a pull-up voltage that is valid. There is a problem with the signal wire between P1 and the harness connector for the sensor. There may be a problem with a connector.

  Repair: Perform the following procedure:

  Disconnect the multimeter leads.

  Use a 151-6320 Wire Removal Tool to remove the jumper wire from the P1 connector.

  Reinstall the terminal that was removed from the P1 connector. Pull on the wire in order to verify proper installation of the terminal.

  Verify that the wiring and/or connectors are OK. Repair any faulty wiring and/or connectors, when possible. Replace any wiring and/or connectors, if necessary. Refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - The pull-up voltage for the suspect sensor at the ECM is not between 6.0 VDC and 7.0 VDC. Proceed to Test Step 6.

Test Step 5. Check the Sensor

1. Temporarily connect a sensor that is known to be good to the engine harness.

2. Observe the "Active Diagnostic" screen on Cat ET. Allow a minimum of 30 seconds for any codes to activate.

Expected Result:

No diagnostic codes are activated.

Results:

• OK - No diagnostic codes are activated when a good sensor is temporarily installed. Connecting a new sensor resolved the problem.

  Repair: Perform the following procedure:

  1. Reconnect the suspect sensor. Verify that the -3 diagnostic code recurs.

  2. Disconnect the suspect sensor. Verify that the -3 diagnostic code is deactivated.

  3. Connect the new connector. Verify that no diagnostic codes are activated.

     If these conditions are true, replace the faulty sensor with the new sensor. For the proper torque value for the new sensor, refer to the Specifications manual.

  4. Clear all of the diagnostic codes. Verify that the problem has been resolved.

  STOP

• Not OK - The active -3 code remains. Connecting a new sensor did not resolve the problem. Proceed to Test Step 6.

Test Step 6. Check the Operation of the ECM

1. Verify that the signal wire for the suspect sensor has been removed from the P1 connector.

2. Clear any existing diagnostic codes.

3. Observe the "Active Diagnostic" screen on Cat ET. Allow a minimum of 30 seconds for any codes to activate.

   An active -3 diagnostic code is generated for the sensor.

4. Use a jumper wire that is the appropriate length with Deutsch terminals on the ends. Install one end of the jumper wire into the terminal for the signal wire that was removed from the P1 connector. Install the other end of the jumper wire into terminal 19 of the P1 connector. This will replace the sensor circuit with a short circuit.

5. Observe the "Active Diagnostic" screen on Cat ET. Allow a minimum of 30 seconds for any codes to activate.

   An active -4 diagnostic code is generated.

Expected Result:

Active -3 and -4 diagnostic codes are generated according to the above steps.

Results:

• OK - Active -3 and -4 diagnostic codes are generated according to the above steps. The ECM is operating correctly. The initial diagnostic code was probably caused by a poor electrical connection.

  Repair: Perform the following procedure:

  Use a 151-6320 Wire Removal Tool to remove the jumper wire from the P1 connector.

  Reinstall the terminal that was removed from the P1 connector. Pull on the wire in order to verify proper installation of the terminal.

  Resume normal operation.

  STOP

• Not OK - No active -3 and -4 diagnostic codes were generated. The ECM is not operating correctly.

  Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this entire procedure again. If the problem is not resolved, perform the following steps:

  Temporarily install a new ECM. Refer to Troubleshooting, "ECM - Replace".

  If the problem is resolved with the new ECM, install the original ECM and verify that the problem returns. If the new ECM operates correctly and the original ECM does not operate correctly, replace the ECM. Refer to Troubleshooting, "ECM - Replace".

  STOP