Component Tests and General Diagnostics

Differential Oil Cooler Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions)provides an overview of each diagnostic category.

Diagnostic Fault Information





Circuit/System Description

The differential cooler is designed to reduce the temperature of the rear differential fluid during high speed driving. The differential cooler system is controlled by a temperature switch (included with the differential cooler kit) located in the rear of the differential housing and functions when conditions require it to operate. The fluid capacity for the rear differential cooler is greater than the standard system.

Reference Information
Schematic Reference

Rear Axle Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning)for scan tool information

Circuit/System Testing

1. Ignition OFF, disconnect the differential cooler pump relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal A2 and ground.

• If the test lamp illuminates, test the control circuit for a short to voltage.

3. Verify that a test lamp illuminates between the ignition circuit terminal C2 and ground.

• If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test or replace the differential cooler switch relay.

4. Verify that a test lamp illuminates between the B+ circuit terminal C1 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal A2 for a short to ground.

5. Disconnect the harness connector at the differential temperature switch. Install a jumper wire between the control circuit terminal A and the ground circuit terminal B.
6. Disconnect the harness connector at the differential cooler pump.
7. Test for less than 5 ohm between the differential cooler pump ground circuit terminal 2 and ground

• If greater than the specified range, test the ground circuit for an open/high resistance.

8. Connect the harness connector at the differential cooler pump.
9. Connect a 20 A fused jumper wire between the B+ circuit terminal C1 and the control circuit terminal A2. Verify the differential cooler pump is activated.
10. If the differential cooler pump does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the differential cooler pump.
11. Connect a test lamp between the ignition circuit terminal C2 and the ground circuit terminal A1.
12. Turn the ignition ON and OFF. The test lamp should turn ON and OFF when changing between the selected states.

• If the test lamp is always OFF, test the ground circuit for an open/high resistance.

13. Ignition OFF, install the differential cooler pump relay.
14. Turn the ignition ON and OFF. The differential cooler pump should turn ON and OFF when changing between the selected states.

• If the differential cooler pump is always OFF, test or replace the differential cooler pump relay.

15. If all circuits test normal, test or replace the differential temperature switch.

Component Testing

Relay Test
1. Ignition OFF, disconnect the differential cooler pump relay.
2. Test for 60-180 ohm between terminals C2 and A1.

• If not within the specified range, replace the differential cooler pump relay.

3. Test for infinite resistance between the following terminals:

* C1 and C2
* C1 and A2
* C1 and A1
* A1 and A2

• If not the specified value, replace the differential cooler pump relay.

4. Test for less than 2 ohm between terminals C1 and A2.

• If greater than the specified range, replace the differential cooler pump relay.

5. Install a 20 A fused jumper wire between relay terminal C2 and B+. Install a jumper wire between relay terminal A1 and ground. Test for less than 2 ohm between terminals C1 and A2.

• If greater than the specified range, replace the differential cooler pump relay.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Differential Oil Cooler Temperature Sensor Replacement (Differential Oil Cooler Temperature Sensor Replacement)
* Differential Cooler Pump Replacement ()