U012ALost Communication With Chassis Control Module A
- Generic OBD-II code · Network
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- U012A reports that chassis control module A is silent. The unit behind the letter A varies between brands; GM uses the code in several engine and transmission tables. The 2016 ECM for the L20 engine waits for message $4DB and logs a missing frame as Type B, so the MIL comes after two trips; the 2020 ten-speed transmission controller watches frame $1F7 from the integrated chassis control module (ICCM) and treats the loss as emissions-neutral Type C. GM's 2015 engine table even uses U012A for a lost fuel pump control module, more than 0.5 s without a message, also Type B. U012B is the B module, U042B invalid data from module A. Effects range from chassis warnings to engine trouble.
- What you may notice
- MIL on in vehicles where the engine controller logs it
- Chassis functions controlled by module A unavailable
- Hard start or stalling if the module drives the fuel pump
- Likely causes
- LikelyPower, ground or fuse of chassis module A missing
- PossibleBus wiring or connector to the module damaged
- PossibleVoltage dip leaving a stored code
- RareChassis module A internally faulty
- Repair
- Medium · Usually a job for a workshop.Typical cost: €60 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.