Chassis Definition only Lights the check engine lamp

C009A: 4WD/AWD Rear Differential Unit Actuator A Position Sensor B

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 C009A mean?

Fault on rear differential actuator A position sensor B.

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 Sensor failed

Likelihood is a general estimate across vehicles; your make and model may differ.

Add your car to see reports of C009A on the same make and model first.

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