C0099: 4WD/AWD Rear Differential Unit Actuator A Position Sensor A
Standardized SAE J2012 code · C00xx codes
Safety-critical system. Faults in airbags, brakes, steering or high-voltage components can put people at risk. Follow the manufacturer's service information and safety procedures, or have the vehicle checked by a qualified workshop.
What does C0099 mean?
The ABS control module fails its internal self-test (RAM, ROM or processor watchdog). ABS and stability control are disabled.
The code tells you which monitor failed, not which part is broken. Test before replacing parts.
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
Common causes
- High Module internally failed
- Medium Power supply undervoltage during operation
Likelihood is a general estimate across vehicles; your make and model may differ.
Add your car to see reports of C0099 on the same make and model first.
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