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
- 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.
- 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.
- 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
- Replace the limited slip differential clutch high pressure pipe.
- Perform the Rear Differential Hydraulic System Service Fill/Bleed.
- 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.
- 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.
- Ignition OFF, disconnect the X2 harness connector at the K47 Rear
Differential Clutch Control Module.
- 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
- 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.
- Ignition OFF, disconnect the X2 harness connector at the K47 Rear
Differential Clutch Control Module,
Ignition ON/Vehicle in Service Mode.
- 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
- Ignition OFF, disconnect the X2 harness connector at the K47 Rear
Differential Clutch Control Module.
- 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
- 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.
- Ignition OFF, disconnect the X2 harness connector at the K47 Rear
Differential Clutch Control Module,
Ignition ON/Vehicle in Service Mode.
- 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
- Disconnect the X2 harness connector at the K47 Rear Differential Clutch
Control Module.
- 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.
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.
READ NEXT:
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.
Diag
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.
Diag
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.
Diag
SEE MORE:
RADIO/NAVIGATION SYSTEM WIRING SCHEMATICS (IOB)
Power, Ground, Serial Data and Subsystem References
Infotainment Display and Radio Controls
Antennas
Speakers
Auxiliary Inputs (MCY)
RADIO/NAVIGATION SYSTEM WIRING SCHEMATICS (IOR)
Power, Ground, Serial Data and Subsystem References
Infotainment
Dome Lamps
The dome lamp controls are in the
overhead console.
To operate, press the following
buttons:
OFF : Press to turn off the
dome lamps when a door is open.
An indicator light on the button will
turn on when the dome lamp
override is activated. Press
OFF again to deactivate this feature