C0420: Adaptive Cruise Control Module Internal Performance
Standardized SAE J2012 code · C04xx 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 C0420 mean?
The adaptive cruise control module has reported an internal performance fault — for example self-test failure, supply voltage out of range or invalid configuration. ACC is 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 ACC module internal fault
- Medium Supply voltage out of range
- Low Module configuration invalid after part exchange
Likelihood is a general estimate across vehicles; your make and model may differ.
Add your car to see reports of C0420 on the same make and model first.
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