C-10 and C-15 Petroleum Engines Caterpillar

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

• Coolant temperature sensor

• Inlet manifold temperature sensor

• Fuel 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

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).

Pull-up Voltage

The ECM continuously outputs a pull-up voltage on the circuit for the sensor signal wire. The ECM uses this pull-up voltage in order to detect an open in the signal circuit. When the ECM detects the presence of a voltage that is above a threshold on the signal wire, the ECM will generate a -03 diagnostic code.

If the sensor is disconnected at the sensor connector, the presence of pull-up voltage at the sensor connector indicates that the signal wire and the return wire from the sensor connector to the ECM are good.

If the sensor is disconnected at the sensor connector, the absence of pull-up voltage at the sensor connector indicates an open in the signal wire, an open in the return wire, or a short to ground.

If the sensor is disconnected at the sensor connector and the voltage on the signal wire at the sensor connector is different from pull-up voltage, the signal wire is shorted to another wire in the harness.

Illustration 1	g01146708
C-10 schematic for temperature sensors

Illustration 2	g01080829
C-15 schematic for temperature sensors

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The connection of any electrical equipment and the disconnection of any electrical equipment may cause an explosion hazard which may result in injury or death. Do not connect any electrical equipment or disconnect any electrical equipment in an explosive atmosphere.

Test Step 1. Inspect Electrical Connectors and Wiring

1. Turn the keyswitch to the OFF position.

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Illustration 3	g01146721
C-10 left side engine view (1) Engine coolant temperature sensor (2) Intake manifold air temperature sensor (3) Fuel temperature sensor (4) J2/P2 ECM connector

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Illustration 4	g01146716
C-15 left side engine view (1) Engine coolant temperature sensor (2) Intake manifold air temperature sensor (3) Fuel temperature sensor (4) J2/P2 ECM connector

2. Thoroughly inspect ECM connectors (4) and the connectors for sensors (1), (2), and (3). Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

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Illustration 5	g01146711
P2 ECM connector (P2-13) Engine coolant temperature (P2-30) Sensor return (P2-56) Intake manifold air temperature (P2-62) Fuel temperature

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Illustration 6	g01146837
2-Pin connector for temperature sensors (typical example) (Pin 1) Sensor signal (Pin 2) Sensor return

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

4. Verify that the latch tab of the connector is properly latched.

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

6. Check the harness and wiring for abrasions and for pinch points from the 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 are OK. Proceed to Test Step 2.

• Not OK - There is a problem in 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 keyswitch to the ON position.

3. Check for active diagnostic codes Cat ET. Record any active diagnostic codes.

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

4. Determine if the problem is related to an open circuit diagnostic code -03 or a short circuit diagnostic code -04.

Expected Result:

No diagnostic codes are active.

Results:

• OK - No diagnostic codes are active.

  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 - A short circuit diagnostic code -04 is active at this time. Proceed to Test Step 3.

• Not OK - An open circuit diagnostic code -03 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 harness at the sensor connector.

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

4. Check Cat ET for an active open circuit diagnostic code -03 for the suspect sensor.

5. Turn the keyswitch to the OFF position.

Expected Result:

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

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: 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 short circuit diagnostic code -04 is still present. The short circuit is between the sensor harness connector and the ECM. 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 (sensor signal) and terminal 2 (sensor return) at the sensor 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 suspect sensor connector.

  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. Verify that the Circuit is not Shorted to a Voltage Source

1. Turn the keyswitch to the OFF position.

2. Disconnect ECM connectors P2 and P1 from the ECM.

3. Disconnect the connector for the sensor at the harness connector.

4. At the ECM, measure the resistance between the terminal for the sensor signal wire and every terminal on ECM connector P1 and P2.

5. Reconnect ECM connectors P1 and P2.

Expected Result:

Each check of the resistance indicates an open circuit.

Results:

• OK - Each measurement indicated an open circuit. Proceed to Test Step 6.

• Not OK - At least one check of the resistance does not indicate an open circuit.

  Repair: The resistance measurement indicates a low resistance between two or more wires. There may be a problem with a connector. Repair the wire and/or the connector, when possible. Replace parts, if necessary. Verify that the 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 terminal 1 and terminal 2 on the connector for the suspect sensor. Connect the jumper on the harness side of the connector.

3. Turn the keyswitch to the ON position.

4. Check for active diagnostic codes Cat ET. Record any active diagnostic codes. Wait at least 15 seconds for activation of the short circuit diagnostic code -04.

5. Remove the jumper wire.

6. Turn the keyswitch to the OFF 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 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 open circuit diagnostic code -03 remains active with the jumper in place. The open circuit is between the ECM and the sensor connector. Proceed to Test Step 7.

Test Step 7. Check the Operation of the ECM

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

   1. Turn the keyswitch to the OFF 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 for the suspect sensor from the P2 ECM connector. Install a jumper wire in place of the signal wire for the suspect sensor.

   4. Remove the wire for the sensor return from the P2 ECM connector. Install a jumper wire in place of the return wire for the suspect sensor.

      Note: Disconnecting the sensor return from the ECM will generate an open circuit diagnostic code for all sensors that are connected to the sensor return. Troubleshoot the original diagnostic code. Delete the logged diagnostic codes when you are finished.

   5. Reconnect the P2 connector.

   6. Turn the keyswitch to the ON position. Monitor Cat ET for an open circuit diagnostic code (-03) for the suspect sensor. Wait at least 15 seconds for activation of the code.

   7. Turn the keyswitch to the OFF position.

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

   1. Short circuit the two jumper wires at the ECM connector for the sensor signal and the sensor return.

   2. Turn the keyswitch to the ON position. Monitor Cat ET for a short circuit diagnostic code (-04) for the suspect sensor. Wait at least 15 seconds for activation of the code.

   3. Turn the keyswitch to the OFF position.

   4. Remove the wire jumpers and replace all wires. Reconnect ECM connectors J2/P2.

Expected Result:

An open circuit diagnostic code -03 is active when the ECM is tested for an open circuit. A short circuit diagnostic code -04 is active when the ECM is tested for a short circuit.

Results:

• OK - The ECM is working properly. The problem is in the wiring between the ECM and the sensor connector. There may be a problem with a 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 open circuit diagnostic code -03 is not active when the sensor signal wire is disconnected. The short circuit diagnostic code -04 is not active when the wire jumper is installed.

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

  STOP