Some owners of 2010-2012 Cadillac SRX vehicles equipped with all-wheel-drive may comment that the “service rear axle” message is displayed on the DIC.
During diagnosis, the technician may find a C0407 sym64 stored in the rear differential clutch control module (CCM). NOTE: GDS diagnostics must be used to confirm what DTC is set in the CCM.
The C0407.64 code is set when the oil is low in the differential clutch. There are several conditions that can cause the differential clutch to be low on fluid:
- Improper filling of the differential clutch during differential clutch filter/gasket service or pump replacement.
- Differential clutch oil leaking into the rear differential through the limited slip differential clutch.
- External leakages on the differential clutch.
Replacing the control module or module kit will not correct this condition. Removing the control module and valve will purge some of the air from the pump motor cavity, which will give a false condition that a new control module was the correct repair.
Follow the procedures below to help diagnose the root cause of the C0407.64 code:
If the vehicle has had a previous filter or pump replacement and the C0407.64 is set, follow the instructions below. If not, proceed to Procedure B.
The differential clutch is properly filled when the fluid level is level with the bottom of the differential clutch cover plug and the pump cavity is full. The pump cavity is full when the pump motor current is between 2.5 to 3.5 amps while the engine is running and the pump motor is running. The current cycles from 0 to 2.5 – 3.5 amps as the pump turns off/on. Both conditions must be met. If the pump motor current is consistently below 2.5 amp, then the pump motor cavity is low on fluid.
If the fluid level is level with the bottom of the differential clutch cover plug and the pump motor current is below 2.5 amp, then the differential clutch pump cavity is empty. If this is the case, the differential clutch needs to have fluid added using the following procedure:
If the vehicle has not had a previous filter or pump replacement, check the RDM for conditions a) and b).
a) No external leakage visible.
b) Rear differential fluid level too high. If overfilled, drain and correct level.
Confirm that either condition c) or d) exists:
c) Differential clutch fluid level too low.
d) Differential clutch fluid level is OK but the differential clutch pump motor current is constantly below 2.5 A (differential clutch fluid level will not be OK if the pump motor currently is below 2.5 A).
If conditions a) and b) exist and either condition c) or d) exists, then the differential clutch oil is leaking past the differential clutch internal seal into the rear differential. The service fix is to replace the limited slip differential clutch only.
Check the vehicle for external leakages. Look for leakage from the differential clutch oil cover (re-tighten bolts or replace the gasket if needed and re-fill). Inspect for leakage from the limited differential clutch pipes. Replace leaking fittings and re-attach pipes using new clips and re-fill. Leakage from the steel balls on the differential clutch requires replacement of the differential clutch assembly.
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