OBD-II code · Chassis
C0420 Adaptive Cruise Control Module Internal Performance
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.
Is it safe to drive with C0420?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelyACC module internal fault
- PossibleSupply voltage out of range
- Less likelyModule configuration invalid after part exchange
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.5–3 h
- Emissions test
- Usually unaffected
- Parts involved
- Acc Module, Vehicle Power Supply, Communication Bus
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.