C00A4Driveline Control Module Rear Differential Unit B Control Circuit Driver
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- Where a rear unit carries a second actuator, for example the second clutch of a twin-clutch module that can drive each rear wheel on its own, the driveline module needs a second output stage, and C00A4 reports a fault in that one. If actuator B is a brushless motor, the stage is a three-phase bridge: automotive gate drivers such as TI's DRV8343-Q1 detect short to battery, short to ground, MOSFET overcurrent and gate driver faults, and offer an offline open-load and short check before the motor is switched on. BorgWarner's latest AWD coupling uses exactly such a brushless motor with integrated electronics. A driver fault on side B leaves actuator A usable, so some systems can keep partial AWD. No manufacturer publishes a C00A4 case; the actuator's own codes are C0097 and C0098.
- What you may notice
- AWD or torque vectoring warning
- One rear clutch or locking function inactive
- Likely causes
- LikelyPhase or supply line of actuator B shorted to ground or battery
- PossibleWinding fault or blocked rotor in actuator B causing overcurrent
- RareFailed output stage B in the module
- Repair
- Hard · Usually a job for a workshop.Typical cost: €80 – €1,300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.