C7 Engine for 584 and 584HD Forwarders and for 525C, 535C, and 545C Wheel Skidders Caterpillar

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

• Intake manifold air temperature sensor

• Coolant 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

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 circuit, the ECM will generate an open circuit diagnostic code (03) for the sensor.

If the sensor is disconnected at the sensor connector, the presence of pull-up voltage at the sensor connector indicates that the wires from the sensor connector to the ECM are not open or shorted to ground. 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 or a short to ground. If the sensor is disconnected at the sensor connector and the voltage at the sensor connector is different from pull-up voltage, the signal wire is shorted to another wire in the harness.

Illustration 1	g01242617
Schematic for the engine temperature sensors

Test Step 1. Inspect Electrical Connectors and Wiring

1. Remove the electrical power from the ECM.

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Illustration 2	g01219566
Sensor locations (typical left side engine view) (1) Engine coolant temperature sensor (2) Intake manifold air temperature sensor

2. Thoroughly inspect the connectors for sensors (1), and (2). Also, thoroughly inspect ECM connector J2/P2. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".

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Illustration 3	g01241124
P2 ECM connector (P2-13) Engine coolant temperature (P2-30) Sensor return (P2-56) Intake manifold air temperature

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Illustration 4	g01155187
Connector for the temperature sensors (1) Sensor signal (2) Sensor 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 screws for each ECM connector for the proper torque. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".

5. Check the harness and the wiring for abrasions and for pinch points from each of the temperature sensors to the ECM connector.

Expected Result:

All connectors, pins, and sockets are completely coupled and 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 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 the Caterpillar Electronic Technician (ET) to the service tool connector.

2. Restore the electrical power to the ECM.

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

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

4. Look for a 03 diagnostic code or a 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 the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect" for additional information.

  STOP

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

• Not OK - A 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. Remove the electrical power from the ECM.

2. Disconnect the suspect sensor from the engine harness.

3. Restore the electrical power to the ECM.

4. Access the "Active Diagnostic Codes" screen on Cat ET and check for an active 03 diagnostic code for the suspect sensor.

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

5. Remove the electrical power from the ECM.

Expected Result:

A 03 diagnostic code is now active for the suspect sensor.

Results:

• OK - A 04 diagnostic code was active before disconnecting the sensor. A 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 new 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 04 diagnostic code is still present. Leave the sensor disconnected. Proceed to Test Step 5.

Test Step 4. Create a Short at the Sensor Connector

1. Remove the electrical power from the ECM.

2. Disconnect the suspect sensor at the sensor connector.

3. Fabricate a jumper wire that can be used to create a short between terminal 1 (signal) and terminal 2 (sensor return) at the suspect sensor's connector. Crimp connector pins to each end of the jumper wire.

4. Install the jumper into the harness side of the sensor connector.

5. Restore the electrical power to the ECM.

6. Access the "Active Diagnostic Code" screen on Cat ET. Check for an active 04 diagnostic code for the suspect sensor.

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

7. Remove electrical power from the engine ECM.

Expected Result:

A 04 diagnostic code is now active for the suspect sensor.

Results:

• OK - A 03 diagnostic code was active before creating the short at the sensor connector. A 04 diagnostic code became active after creating the short at the sensor connector.

  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 new sensor. If there are no active diagnostic codes for the sensor, permanently install the new sensor. Clear any logged diagnostic codes.

  STOP

• Not OK - A 03 diagnostic code is still active for the suspect sensors. Proceed to Test Step 5.

Test Step 5. Check the Operation of the ECM

1. Remove the electrical power from the ECM.

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

   1. Disconnect the ECM connector for the suspect sensor.

   2. Fabricate a jumper wire that is long enough to reach from a terminal at the ECM connector to the engine ground stud. Crimp a connector socket to one end of the jumper wire.

   3. Remove the signal wire for the suspect sensor from the ECM connector. Install the jumper wire into the terminal location for the signal wire of the suspect sensor.

   4. Connect the ECM connectors.

   5. Restore the electrical power to the ECM.

   6. Monitor the "Active Diagnostic Code" screen on Cat ET. Wait at least 30 seconds for activation of the code.

      An open circuit diagnostic code (03) will be active for the suspect sensor.

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

   1. Short the jumper wire that is installed into the ECM connector to engine ground.

   2. Monitor the "Active Diagnostic Code" screen on Cat ET. Wait at least 30 seconds for activation of the code.

      A short circuit diagnostic code (04) will be active for the suspect sensor.

   3. Remove the electrical power from the ECM.

4. Remove the wire jumper. Reconnect all wires and connectors.

Expected Result:

A 03 diagnostic code is active when the sensor signal wire is open. A 04 diagnostic code is active when the jumper wire is shorted to engine 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. Verify that the repair eliminates the problem.

  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 electronic troubleshooting Troubleshooting, "Replacing the ECM". Verify that the original problem is resolved.

  STOP