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MikeB85
MikeB85, ASE Certified Technician
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Experience:  ASE Certified, I-Car Trained and Certified, Automotive Technology Degree
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AWD light is on constantly, I recently took it to

Resolved Question:

AWD light is on constantly, I recently took it to the dealership where they changed the oil in the rear axle and stated nothing was wrong. Air pressure is equal in both tires which by the way are the same size, I am not running a spare. However, the light is still on and I was wondering if there was a sensor that could possibly be bad that I could change. Any ideas?
Submitted: 6 years ago.
Category: Car
Expert:  MikeB85 replied 6 years ago.

Hi there,

Can you tell me what year, make, and model the vehicle is?

Let me know and I will see if I have the info to help you out. Thanks.

Customer: replied 6 years ago.
2004, Pontiac, Montana with 35,000 mi. I am the original owner.
Expert:  MikeB85 replied 6 years ago.

Hi there,

I am assuming you mean the AWD malfunction light. There are a couple things that could cause this to come on but the main thing would be what is called differential clutch actuator check valve. There are also a few tests that need to be performed to properly diagnose the problem. I also found a bulletin and a brief description of the problem that I will list below. I don't know if you are planning on repairing this yourself or are taking it to dealer but if you need the testing procedures I can provide you with them as well. I hope this helps. Please let me know if you have any questions. Thanks.

MikeB85, ASE Certified Technician
Category: Car
Satisfied Customers: 354
Experience: ASE Certified, I-Car Trained and Certified, Automotive Technology Degree
MikeB85 and 16 other Car Specialists are ready to help you
Expert:  MikeB85 replied 6 years ago.
All-Wheel Drive Disabled Indicator Always On

Circuit Description

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.

Conditions for Running the All-Wheel Drive (AWD) Disable Fault

The system voltage is 9-18 volts.
The engine speed is greater than 500 RPM for 5 seconds, and the engine is not in fuel shut-off.
The rear drive module must not be in an overtemperature condition.

Conditions for Turning On the All-Wheel Drive (AWD) Disable Lamp

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

The PCM commands the solenoid ON and the voltage feedback remains high, B+.
The PCM commands the solenoid OFF and the voltage feedback remains low, 0 volts. This condition is present for 3 key cycles.

Action Taken When the All-Wheel Drive (AWD) Lamp Illuminates

The PCM does not illuminate the malfunction indicator lamp (MIL).
The PCM inhibits AWD.
The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Failure Records.
The PCM stores the AWD disable fault in PCM history.

Conditions for Clearing the All-Wheel Drive (AWD) Disable Fault

A scan tool can clear the fault.
The PCM clears the fault from PCM history if the vehicle completes 40 warm-up cycles without a non-emission related diagnostic fault occurring.
The PCM cancels the fault default actions when the fault no longer exists.

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

Expert:  MikeB85 replied 6 years ago.
#PIP4157: All Wheel Drive Disable Lamp On - keywords AWD inoperative light MIL - (Jun 19, 2007)

Subject:All Wheel Drive Disable Lamp On

Models:2002-2006 Buick Rendezvous
2005-2006 Buick Terraza
2002-2005 Chevrolet Venture
2005-2006 Chevrolet Uplander
2002-2003 Oldsmobile Silhouette
2001-2005 Pontiac Aztek
2002-2005 Pontiac Montana
2005-2006 Pontiac Montana SV6
2005-2006 Saturn Relay
Equipped With All Wheel Drive (AWD)

 



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

Condition/Concern:

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

Recommendation/Instructions:

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.

Customer: replied 6 years ago.
Mike,
I am planning on doing the repair myself. What are the tests you are talking about?
Expert:  MikeB85 replied 6 years ago.
Well I will provide you with the diagnostic chart but unfortunately you will need a digital voltmeter and a Class 2 scan tool to do some of the testing. You can try just replacing the part but without the proper testing and diagnostics it will just be a guess and might not even be the problem at all. This is why shop diagnostic fees are so much. I will give you the chart anyways to give you an idea of what needs to be performed in order to figure out the problem. I hope this helps. Thanks.
Expert:  MikeB85 replied 6 years ago.
All-Wheel Drive (AWD) System Functional Inspection

Functional Inspection 1

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:

The clutch pump check valve is in the "open" position.
The left and right side gerotor pumps have the ability to "pull" fluid from the sump and send pressurized fluid to the left and right side clutch pack pistons.
The left and right side pistons will engage the specific side clutch packs.
There is a mechanical connection between the rear differential ring and pinion, the propeller shaft, the transfer case, and the transmission assembly.
  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

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:

The clutch pump check valve is in the "open" position.
The left and right side gerotor pumps have the ability to "pull" fluid from the sump and send a variable and progressive rate of pressurized fluid to the left and right side clutch pack pistons.
The left and right side pistons will engage the specific side clutch packs at a progressive rate.
There is a mechanical connection between the rear differential ring and pinion, the propeller shaft, the transfer case, and the transmission assembly.
  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

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:

The clutch pump check valve is in the "open" position.
The left and right side gerotor pumps have the ability to "pull" fluid from the sump and send a variable and progressive rate of pressurized fluid to the left and right side clutch pack pistons.
The left and right side pistons will engage the specific side clutch packs at a progressive rate.
The rear differential has the ability to provide rear wheel torque and override the resistance created by the parking brake assembly.
There is a mechanical connection between the rear differential ring and pinion, the propeller shaft, the transfer case, and the transmission assembly.
  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.
Expert:  MikeB85 replied 6 years ago.

Step

Action

Value(s)

Yes

No

Schematic Reference: Differential Lock Schematics

1

Did you perform the Diagnostic System Check - Rear Axle Controls?

--

Go to Step 2

Go to Diagnostic System Check - 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 in Wiring Systems

Go to Step 3

3

  1. Disconnect the differential clutch pump actuator check valve.
  2. Turn ON the ignition, with the engine OFF.
  3. 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 7

4

  1. Connect a test lamp between the ignition 1 voltage circuit and the ground circuit at the differential clutch pump actuator check valve.
  2. Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

--

Go to Step 5

Go to Step 8

5

  1. Turn the ignition OFF.
  2. With the connector connected, connect a DMM in parallel to the control circuit. Set the DMM to read 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.

  1. Start the engine.
  2. 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 9

Go to Step 6

6

Test the axle actuator control circuit for an open, short to voltage, or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 11

Go to Step 10

7

Locate and repair an open or short to ground in the ignition 1 voltage circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 11

--

8

Locate and repair an open in the ground circuit. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 11

--

9

Replace the differential clutch pump actuator check valve. Refer to Differential Clutch Pump Check Valve Replacement

Did you complete the replacement?

--

Go to Step 11

--

10

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls-3.4L.

Did you complete the replacement?

--

Go to Step 11

--

11

  1. Use the scan tool in order to clear the faults.
  2. Operate the vehicle within the Conditions for Running the All-Wheel Drive (AWD) Disable Fault, as specified in the supporting text.

Does the fault set?

--

Go to Step 3

Go to All-Wheel Drive (AWD) System Functional Inspection

 

Customer: replied 6 years ago.
Mike,
     That is indepth. I looked in my Haynes book and the differential clutch pump is not listed. Can you tell me where this part is located on the vehicle? Do you have any idea what it costs? I have taken it to two different dealers that have both changed the fluid and said they could not find anything wrong despite the light. At a charge of around 300.00 per visit. Which has led me here.
Expert:  MikeB85 replied 6 years ago.

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


    Object Number: 630684  Size: SH

  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


    Object Number: 630684  Size: SH

    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.
Customer: replied 6 years ago.
Thank you very much for the help. I am going to give this a whirl.

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