Buick Regal: DTC C0393

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC C0393

• Rear Differential Clutch Solenoid Valve Control Circuit
• For symptom byte information, refer to Symptom Byte List

Diagnostic Fault Information

Circuit/System Description

The right and left rear differential clutch solenoid valves are electro-hydraulic valves used to relieve pressure in the hydraulic system. When the solenoid valves are energized, the valves are closed and hydraulic pressure can be accumulated. When the solenoid valves are de-energized, the valves are open and it is not possible to build hydraulic pressure.

Conditions for Running the DTC

• The engine is running.
• Battery voltage is between 9-16 V.
• DTC C0800 is not current.

Conditions for Setting the DTC

C0393 01

The rear differential clutch control module determines a short to battery on the rear differential clutch solenoid valve control circuit.

C0393 02

The rear differential clutch control module determines a short to ground on the rear differential clutch solenoid valve control circuit.

C0393 5A

The rear differential clutch control module determines a signal plausibility failure.

C0393 61

The rear differential clutch control module determines the differential clutch pump is stuck.

Action Taken When the DTC Sets

One or more of the following actions may occur:

• The electronic limited slip system is temporary inhibited for the duration of the key cycle.
• The electronic limited slip system is disabled for the duration of the key cycle.
• The AWD SERVICE message in the driver information center.

Conditions for Clearing the DTC

• The condition for the DTC is no longer present.
• The DTC is not detected in 40 consecutive drive cycles.

Reference Information

Schematic Reference

Rear Axle Wiring Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEW INDEX

Description and Operation

Rear Drive Axle Description and Operation

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Verify that DTC C0393 with symptom byte 01, 02 or 5A is not set.

• If the DTC is set

Refer to Circuit/System Testing.

• Go to next step: If the DTC is not set

2. Verify that DTC C0393 61 is not set.

• If the DTC is set.

1. Perform the Rear Differential Hydraulic System Bleed Procedure with a scan tool. Refer to Rear Differential Hydraulic System Service Fill/Bleed
2. NOTE: The Rear Differential Clutch Module can run this procedure up to 3 attempts to get a Pass.
3. Verify that DTC C0393 61 is not set.
   • if DTC is set, test or replace the appropriate rear differential clutch solenoid valve.
   • Go to next step: If the DTC is not set
4. All OK.

• Go to next step: If the DTC is not set

3. All OK.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the Q49 Rear Differential Clutch Solenoid Valve, Ignition ON/Vehicle in Service Mode.

2. Test for 5.6 - 6.4 V between the control circuit terminal 3 and ground.

• If less than 5.6 V

1. Ignition OFF, disconnect the X2 harness connector at the K47 Rear Differential Clutch Control Module.
2. Test for infinite resistance between the control circuit terminal 3 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the control circuit terminal 3 end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K47 Rear Differential Clutch Control Module.

• If greater than 6.4 V

1. Ignition OFF, disconnect the X2 harness connector at the K47 Rear Differential Clutch Control Module, Ignition ON/Vehicle in Service Mode.
2. Test for less than 1 V between the control circuit terminal 3 and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K47 Rear Differential Clutch Control Module.

• Go to next step: If between 5.6 - 6.4 V

3. Test for 4.9 - 5.3 V between the control circuit terminals listed below and ground.

• Control Circuit Terminal 2
• Control Circuit Terminal 1
• If less than 4.9 V

1. Ignition OFF, disconnect the X2 harness connector at the K47 Rear Differential Clutch Control Module.
2. Test for infinite resistance between the appropriate control circuit terminal and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the control circuit terminal end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K47 Rear Differential Clutch Control Module.

• If greater than 5.3 V

1. Ignition OFF, disconnect the X2 harness connector at the K47 Rear Differential Clutch Control Module, Ignition ON/Vehicle in Service Mode.
2. Test for less than 1 V between the appropriate control circuit terminal and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K47 Rear Differential Clutch Control Module.

• Go to next step: If between 4.9 - 5.3 V

4. Test or replace the Q49 Rear Differential Clutch Solenoid Valve.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Differential Carrier Assembly Replacement
• Control Module References for control module replacement, programming, and setup.

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