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.
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.
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
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:
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:
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:
Important: Do not accelerate the vehicle with the parking brake applied for a period longer than 5-7 seconds.
Schematic Reference: Differential Lock Schematics
Did you perform the Diagnostic System Check - Rear Axle Controls?
Go to Step 2
Go to Diagnostic System Check - Locking/Limited Slip Rear Axle
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
Does the voltage measure within the specified value?
Go to Step 4
Go to Step 7
Does the test lamp illuminate?
Go to Step 5
Go to Step 8
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.
Is the duty cycle functioning as described?
HI Range: 49-90%
LO Range: 16-28%
Go to Step 9
Go to Step 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
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?
Locate and repair an open in the ground circuit. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.
Replace the differential clutch pump actuator check valve. Refer to Differential Clutch Pump Check Valve Replacement
Did you complete the replacement?
Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls-3.4L.
Does the fault set?
Go to All-Wheel Drive (AWD) System Functional Inspection
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
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.
Notice: Refer to Fastener Notice in the Preface section.
Tighten Tighten the bolts to 10 N·m (89 lb in).