Buick Regal: DTC C0407

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 Descriptors

DTC C0407

Differential Oil Pump Motor

For symptom byte information, refer to Symptom Byte List.

Diagnostic Fault Information

Circuit/System Description

The pressure in the hydraulic circuit is controlled by the differential clutch pump. The differential clutch pump utilizes a brushless motor and a radial piston pump. The motor in the differential clutch pump is controlled utilizing a bi-directional control that applies power and ground to each control circuit. By reversing the polarity of the motor, the differential clutch pump is able to spin both clockwise and counter-clockwise as a means to increase and decrease pressure in the system. The differential clutch pump is constantly increasing or decreasing the pressure in the system according to the torque request signal as controlled by the rear differential clutch control module.

Conditions for Running the DTC

C0407 01, C0407 02, C0407 1B, C0407 5A

• The engine is running.
• Battery voltage is between 9-16 V.
• The engine speed is above 400 rpm.

C0407 04

• The engine is running.
• The starter motor commanded on is false.
• Battery voltage is between 9-16 V.
• The engine speed is above 400 rpm.

C0407 0B, C0407 61, C0407 64

• The engine is running.
• The engine speed is above 400 rpm.

Conditions for Setting the DTC

C0407 01

When voltage for motor phase U, V, and W is above 1.0 V.

C0407 02

When voltage for motor phase U, V, and W is below 7.0 V.

C0407 04

When voltage for motor phase U, V, and W is below 7.0 V.

C0407 0B

The bridge driver circuit detects shunt voltage above 0.16 V.

C0407 1B

A rear differential clutch control module has detected a short between U, V, and W phases.

C0407 5A

The rear differential clutch control module detects implausible voltage reading.

C0407 61

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

C0407 64

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

Action Taken When the DTC Sets

• Electronic limited slip is disabled for the duration of the key cycle.
• The AWD SERVICE message is displayed 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 ignition 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 DTC C0407 with symptom byte 01, 02 or 04 is not set.

• If any of the DTCs are set

Refer to Circuit/System Testing.

• Go to next step: If none of the DTCs are set

2. Verify the differential clutch fluid level is correct. Refer to Rear Axle Lubricant Level Inspection.

• If the differential clutch fluid level is below specifications

1. Verify the rear axle lubricant level is correct. Refer to Rear Axle Lubricant Level Inspection.

NOTE: If the vehicle is unable to complete the rear differential hydraulic system service fill/bleed procedure, the M32 Differential Clutch Pump may have been damaged by the low differential clutch fluid level.

• If the rear axle lubricant level is above specifications, the differential clutch may be leaking differential clutch oil into the rear axle lubricant. Inspect for and correct any internal fluid leaks between the differential clutch oil and the rear axle lubricant. Refer to Rear Differential Carrier Leak Diagnosis.
• If the rear axle lubricant level is below specifications, inspect for fluid leaks and fill as required.
• Go to next step: If the rear axle lubricant level is correct.

2. Verify there are no external differential clutch oil leaks.
   • If any external differential clutch oil leaks are observed, repair as necessary. Refer to Rear Differential Carrier Leak Diagnosis.
   • Go to next step: If there are no external differential clutch oil leaks.
3. All OK.

• Go to next step: If the differential clutch fluid level is correct

3. Verify DTC C0407 with symptom byte 61 or 64 is not set.

• If any of the DTCs are set

4. Verify the limited slip differential clutch high pressure pipe has not been damaged.

• If the limited slip differential clutch high pressure pipe has been damaged

1. Replace the limited slip differential clutch high pressure pipe.
2. Perform the Rear Differential Hydraulic System Service Fill/Bleed.
3. Verify the vehicle is able to complete the rear differential hydraulic system service fill/bleed procedure.
   • If the vehicle is unable to complete the rear differential hydraulic system service fill/bleed procedure, perform the Rear Differential Hydraulic System Service Fill/Bleed two additional times. If the vehicle is unable to complete the rear differential hydraulic system service fill/bleed procedure after three attempts, refer to Circuit/System Testing.
   • Go to next step: If the vehicle is able to complete the rear differential hydraulic system service fill/bleed procedure.
4. Verify DTC C0407 with symptom byte 61 or 64 is not set
   • If any of the DTCs are set, refer to Circuit/System Testing.
   • If none of the DTCs are set, all OK.

• Go to next step: If the limited slip differential clutch high pressure pipe has not been damaged

Go to next step: Refer to Circuit/System Testing.

• Go to next step: If none of the DTCs are set

5. All OK.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the M32 Differential Clutch Pump, Ignition ON/Vehicle in Service Mode.

2. Test for 5.3 - 5.7 V between the control circuit terminal 6 and ground.

• If less than 5.3 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 6 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 6 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 5.7 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 6 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 5.3 - 5.7 V

3. Test for 2.6 - 3.0 V between the control circuit terminals listed below and ground.

• Control Circuit Terminal 7
• Control Circuit Terminal 8
• If less than 2.6 V

1. Ignition OFF, disconnect the X2 harness connector at the K47 Rear Differential Clutch Control Module.
2. Test for infinite resistance between the 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 3.0 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 2.6 - 3.0 V

4. Ignition OFF, disconnect the scan tool and disconnect the harness connector at the M32 Differential Clutch Pump.

5. Test for greater than 25 Ω between the following control circuit terminals listed below.

• Control Circuit Terminal 6
• Control Circuit Terminal 7
• Control Circuit Terminal 8
• If 25 Ω or less

1. Disconnect the X2 harness connector at the K47 Rear Differential Clutch Control Module.
2. Test for infinite resistance between the three control circuits.
   • If less than infinite resistance, repair the short between the three circuits.
   • If infinite resistance, replace the K47 Rear Differential Clutch Control Module.

• Go to next step: If greater than 25 Ω

6. Test or replace the M32 Differential Clutch Pump.

7. Operate the vehicle under the conditions for setting the DTC, the DTC should not set.

• If the DTC sets

Replace the K47 Rear Differential Clutch Control Module.

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

8. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Limited Slip Differential Clutch High Pressure Pipe Replacement
• Differential Carrier Assembly Replacement for M32 Differential Clutch Pump.
• Control Module References for control module replacement, programming and setup.

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