GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The differential lock indicator lamp is located in the instrument panel cluster (IPC). Ignition 3 voltage is supplied to the differential lock indicator through the differential lock solenoid valve feed circuit when the ignition switch is in the START or RUN position and the differential lock switch is engaged. Ground is supplied through the ground circuit to splice pack 2.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step tests for an intermittent condition.

  2. This step tests the differential lock portion of the circuit.

  3. This steps tests for proper voltage at the IPC.

  4. This step tests the differential lock indicator ground circuit.

Step

Action

Value

Yes

No

Schematic Reference: Differential Lock Schematics

1

Did you review the Differential Lock Description and Operation and perform the necessary inspections?

--

Go to Step 2

Go to Symptoms - Locking/Limited Slip Rear Axle

2

Verify the fault is present.

Does the system operate normally?

--

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3

Does the differential lock solenoid energize when the switch is energized?

--

Go to Step 4

Go to Differential Lock Inoperative

4

  1. Turn ON the ignition, with the engine OFF.
  2. Turn the differential lock switch ON.
  3. Test the differential lock solenoid valve feed circuit for proper voltage at the instrument panel cluster (IPC).

Does the voltage measure within the specified value?

9-14 V

Go to Step 5

Go to Step 6

5

Connect a test lamp from the differential lock solenoid valve feed circuit to the ground circuit at the IPC.

Did the test lamp light?

--

Go to Step 7

Go to Step 8

6

Repair the open or high resistance in the differential lock solenoid valve feed circuit. Refer to Circuit Testing and Wiring Repairs.

Did you complete the repair?

--

Go to Step 9

--

7

Replace the IPC. Refer to Instrument Cluster Replacement.

Did you complete the replacement?

--

Go to Step 9

--

8

Repair the open or high resistance in the differential lock indicator ground circuit. Refer to Circuit Testing and Wiring Repairs.

Did you complete the repair?

--

Go to Step 9

--

9

Operate the vehicle within the conditions for causing the symptom as specified in the supporting text.

Does the system operate normally?

--

System OK

Go to Step 2