Test Description

WARNING: This page is about a different car, the 2006 Pontiac Montana SV6, 2006 Chevrolet Uplander, and 2006 Buick Terraza. However, it is still accessible from the selected car via links, so may be relevant.

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

3: This step tests the ignition 1 voltage circuit for proper voltage.
4: This step tests the ground circuit for an open.
5: This step tests the axle actuator control circuit duty cycle.
6: This step tests the axle actuator control circuit for an open or short.

Differential Lock Inoperative

Step	Action	Values	Yes	No
Schematic Reference: All-Wheel Drive Schematics
1	Did you perform the Diagnostic System Check - Vehicle?	-	Go to Step 2	Go to Diagnostic System Check - Vehicle
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	Disconnect the differential clutch pump actuator check valve. Turn ON the ignition, with the engine OFF. Using a DMM, test the ignition 1 voltage circuit for proper voltage. Does the voltage measure within the specified value?	9-14 V	Go to Step 4	Go to Step 8
4	Connect a test lamp between the ignition 1 voltage circuit and the ground circuit at the differential clutch pump actuator check valve. Turn ON the ignition, with the engine OFF. Does the test lamp illuminate?	-	Go to Step 5	Go to Step 9
5	Turn the ignition OFF. With the connector connected, connect a DMM in parallel to the axle actuator control circuit and the ground circuit. Set the DMM to measure duty cycle. IMPORTANT: The differential clutch pump actuator check valve duty cycle will initiate at 49-90 percent duty cycle for 3 seconds, then drop to 16-28 percent duty cycle. Every 30 seconds, the duty cycle will cycle up to 49-90 percent for 0.5 seconds, then back to 16-28 percent. Start the engine. Observe AWD Duty Cycle on the DMM from the time of engine start. Is the duty cycle functioning as described?	HI Range: 49-90% LO Range: 16-28%	Go to Step 10	Go to Step 6
6	Test the axle actuator control circuit for the following conditions: An open A short to voltage A short to ground Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	-	Go to Step 12	Go to Step 7
7	Verify that the differential clutch pump actuator check valve connector is securely fastened. Using a scan tool, check the status of the following conditions: AWD Minispare Disable AWD Fluid Temp Disable Did you find and correct the conditions?	-	Go to Step 12	Go to Step 11
8	Locate and repair an open or a short to ground in the ignition 1 voltage circuit. Refer to Circuit Testing and Wiring Repairs . Did you complete the repair?	-	Go to Step 12	-
9	Locate and repair an open in the ground circuit. Refer to Testing for Continuity and Wiring Repairs . Did you complete the repair?	-	Go to Step 12	-
10	Replace the differential clutch pump actuator check valve. Refer to Differential Clutch Pump Check Valve Replacement . Did you complete the replacement?	-	Go to Step 12	-
11	Replace the PCM for 3.5L or the TCM for 3.9L. Refer to Control Module References for replacement, setup and programming. Did you complete the replacement?	-	Go to Step 12	-
12	Turn the ignition ON, with the engine OFF. With the differential clutch pump actuator check valve removed, command the valve ON, then OFF. Refer to Differential Clutch Pump Check Valve Replacement . Does the differential clutch pump actuator check valve move within the listed parameters?	2 mm	Go to Step 13	Go to Step 3
13	Does the AWD system operate normally?	-	System OK	Go to All-Wheel Drive (AWD) System Functional Inspection