U042B code meaning
Invalid Data Received From Chassis Control Module A
What U042B means
Chassis control module A is a generic name for a controller that coordinates chassis functions, and the job behind the letter varies by brand. GM's documents give one concrete owner: the 2020 ten-speed transmission controller (20OBDG03A) treats the integrated chassis control module (ICCM) as chassis control module A and watches its frame $1F7; an L20 engine controller of 2016 also listens to this module. U042B is set when such frames keep arriving but fail content checks, as opposed to U012A, where they stop. No manufacturer documents U042B publicly, so thresholds and lamp behaviour remain open; GM rates the missing-frame case Type C on the transmission and Type B on the engine. Expect chassis or stability messages and a degraded function; a MIL depends on which controller stores it. U042C is module B.
U042B at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor0.3 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U042B
- Chassis, stability or suspension warning
- Chassis functions such as damping or traction aids limited
Common causes of U042B
- PossibleSoftware fault in the chassis module or the receiving controller
- PossibleLow voltage or reset of the chassis module during operation
- Less likelyChassis control module A faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Chassis module a
What each part of U042B means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 2B | The exact fault in that area. |
What to do next
- Note U042B 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 U042B
What does U042B mean?
U042B means "Invalid Data Received From Chassis Control Module A". Chassis control module A is a generic name for a controller that coordinates chassis functions, and the job behind the letter varies by brand. It is a generic code, so it means the same on every make.
Is it safe to drive with U042B?
Drive gently and only to a workshop. With U042B the car can go into limp mode (reduced power) to protect itself.
Will U042B fail an emissions test?
U042B 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 U042B to fix?
Difficulty: workshop only. A typical repair takes 0.3 to 2.5 hours of work. This is a job for a workshop.
Will U042B clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.