The differential clutch pump actuator check valve assembly is a pulse width modulated actuator mounted to the rear drive assembly. Ignition voltage is supplied to the clutch pump actuator check valve through a fused circuit. The PCM controls the actuator with a negative duty cycle. The actuator controls the supply fluid to the pump inlet in the rear drive assembly. When the actuator is commanded OFF, the PCM will detect a high voltage. When the actuator is commanded ON, the PCM will detect a low voltage. At engine start-up, the actuator is turned ON at 49-90 percent duty cycle for 3 seconds, then drops to 16-28 percent for holding. Every 30 seconds, the duty cycle is ramped to 49-90 percent for 0.5 second, then back to 16-28 percent. If the PCM detects a voltage on the axle actuator circuit that is outside of the calibrated limits then the all-wheel drive (AWD) disable lamp illuminates.

The AWD disable lamp illuminates when one of the following conditions exists for 5 seconds:

Important: When an AWD mini spare disable condition is present, after correcting the condition, the vehicle must be driven 0.5 km (0.3 mi) in a straight line and then brought to a complete stop before the PCM will command the AWD disable lamp

	View Full Image

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Customer may comment on an all wheel drive (AWD) disable lamp on, technician may find no codes in any module.

If eSI diagnostics do not lead to a resolution inspect connector C305 and C305B at the body pass through for corrosion, if no corrosion is found suspect the differential clutch pump actuator check valve as the possible cause.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

Functional Inspection 1 is a mechanical system inspection for both the left and right side gerotor pumps, pistons, and clutch packs and will assist in determining if:

1. Raise the vehicle on a hoist. Lift the vehicle in a manner that will allow all four wheels to rotate during testing.
2. Start the engine.
3. Move the gear shift lever to the NEUTRAL position.
4. Rotate, by hand, a rear wheel in a forward direction. If the All-Wheel Drive (AWD) system mechanical components are functioning properly, the front wheels will rotate at the same speed.
5. Rotate, by hand, the opposite side rear wheel. If the All-Wheel Drive (AWD) system mechanical components are functioning properly, the front wheels will rotate at the same speed. Failure of the front wheels to rotate during this test may indicate a "closed" clutch pump check valve, malfunctioning gerotor pump, piston, clutch pack, or valves internal to the unit.

Functional Inspection 2 is a mechanical system inspection for both the left and right side gerotor pumps, pistons, and clutch packs and will assist in determining if:

1. Raise the vehicle on a hoist. Lift the vehicle in a manner that will allow all four wheels to rotate during testing.
2. Start the engine.
3. The gear shift lever should be in the PARK position.
4. Rotate, by hand and in a forward direction, a rear wheel at a slow rate of speed. Rotation of the wheel should be possible.
5. Rotate, by hand and in a forward direction, the opposite side rear wheel at a slow rate of speed. Rotation of the wheel should be possible.
6. Rotate, by hand and in a forward direction, a rear wheel at a fast rate of speed. A properly operating pump, piston, and clutch pack will activate and create a progressive increase in wheel rotational resistance.
7. Rotate, by hand and in a forward direction, the opposite side rear wheel at a fast rate of speed. A properly operating pump, piston, and clutch pack will activate and create a progressive increase in wheel rotational resistance. Failure to feel a progressive rate of resistance may indicate a "closed" clutch pump check valve, malfunctioning gerotor pump, piston, clutch pack, or valves internal to the unit.

Functional Inspection 3 is a mechanical system inspection for both the left and right side gerotor pumps, pistons, and clutch packs and will assist in determining if:

1. Raise the vehicle on a hoist. Lift the vehicle in a manner that will allow all four wheels to rotate during testing.
2. Start the engine.
3. Move the gear shift lever to the DRIVE position.
4. Accelerate the vehicle lightly until all four wheels are rotating at an equal slow speed.
5. Depress the parking brake slightly, gradually increasing the parking brake retention to create resistance in the rear wheels. The rear wheels should stop spinning. The front wheels should remain spinning.

   Important: Do not accelerate the vehicle with the parking brake applied for a period longer than 5-7 seconds.

6. Lightly depress the accelerator pedal, increasing engine rpms in order to determine if the rear wheels can provide enough torque to "override" the resistance created by the parking brake assembly. Failure of the rear wheels to rotate during this test may indicate a "closed" clutch pump check valve, malfunctioning gerotor pump, piston, clutch pack, or valves internal to the unit.

I know it seems like a lot to do the testing and without the proper tools as well as the scan tool it makes it very difficult. Here is the procedure for replacing the differential clutch pump check valve. Again I can't guarantee that this is the problem but it is a possibility.

Differential Clutch Pump Check Valve Replacement

Removal Procedure

	View Full Image




1. Drain the differential lubricant. Refer to Lubricant Change in Rear Drive Axle.
2. Disconnect the clutch pump check valve electrical connector.
3. Remove the clutch pump check valve mounting bolts (4, 5).
4. Remove the clutch pump check valve (3) by carefully pulling straight out of the differential carrier.
5. Remove the O-ring seals (1, 2) from the valve. The O-ring seals may be reused if not cut or damaged.

Installation Procedure

	View Full Image





Important: Inspect the clutch pump check valve O-ring seals in order to ensure they are not cut or damaged. Replace cut or damaged O-ring seals with new seals.

1. Lubricate the O-ring seals (1, 2) with synthetic gear oil GM P/N 12378514 (Canadian P/N 88901045) or equivalent.
2. Install the O-ring seals to the valve.

   Notice: Refer to Fastener Notice in the Preface section.

3. Install the clutch pump check valve to the differential carrier by carefully pushing the valve straight in until fully seated.
4. Install the clutch pump check valve mounting bolts (4, 5).

   Tighten
   Tighten the bolts to 10 N·m (89 lb in).

5. Connect the clutch pump check valve electrical connector.
6. Fill the rear differential lubricant. Refer to Lubricant Change in Rear Drive Axle.