U042C code meaning
Invalid Data Received From Chassis Control Module B
What U042C means
U042C refers to a second chassis controller, labelled B, where chassis tasks are split between two units. It is stored when that module's frames still arrive but carry a bad counter, checksum or implausible values. No manufacturer documents U042C or the B module publicly; the only public assignment found concerns module A, which GM's 2020 transmission tables equate with the integrated chassis control module. CARB asks emission-related controllers to flag faulty digital communication as well as its absence, which mirrors the pair U012B and U042C, although a chassis unit usually lies outside that rule. B alone points to that module or its harness, B with U042B to shared supply, gateway or bus wiring. A MIL is not expected; chassis messages are likely. U012B is lost contact.
U042C 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 U042C
- Chassis or suspension warning in the cluster
- Chassis function handled by module B inactive
Common causes of U042C
- PossibleSoftware fault in chassis module B or the receiver
- PossibleSupply, ground or gateway problem affecting the module's messages
- Less likelyChassis control module B faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Chassis module b
What each part of U042C means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 2C | The exact fault in that area. |
What to do next
- Note U042C 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 U042C
What does U042C mean?
U042C means "Invalid Data Received From Chassis Control Module B". U042C refers to a second chassis controller, labelled B, where chassis tasks are split between two units. It is a generic code, so it means the same on every make.
Is it safe to drive with U042C?
Drive gently and only to a workshop. With U042C the car can go into limp mode (reduced power) to protect itself.
Will U042C fail an emissions test?
U042C 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 U042C 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 U042C clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.