U012A code meaning
Lost Communication With Chassis Control Module A
Network system Generic code U01xx codes Check engine light
What U012A means
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.
U012A at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U012A
- 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
Common causes of U012A
- Most likelyPower, ground or fuse of chassis module A missing
- PossibleBus wiring or connector to the module damaged
- PossibleVoltage dip leaving a stored code
- Less likelyChassis module A internally faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Chassis module aCAN bus wiring
What each part of U012A means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 2A | The exact fault in that area. |
What to do next
- Note U012A and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U012A
What does U012A mean?
U012A means "Lost Communication With Chassis Control Module A". U012A reports that chassis control module A is silent. It is a generic code, so it means the same on every make.
Is it safe to drive with U012A?
Drive gently and only to a workshop. With U012A the car can go into limp mode (reduced power) to protect itself.
Will U012A fail an emissions test?
U012A is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U012A to fix?
Difficulty: medium. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will U012A clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.