U0442 code meaning
Invalid Data Received From ECM/PCM B
Network system Generic code U04xx codes Check engine light
What U0442 means
ECM/PCM B stands for a second engine or powertrain controller where a car carries more than one such unit; U0442 means its frames reach a receiver with invalid content, while U0115 means they stop arriving. Mazda applies the code in its own way: bulletin 01-015/18 for the 2018 Mazda6 and CX-5 and the 2019 CX-3 and MX-5 describes the TCM of automatic models flagging invalid PCM data, together with P061B and U0401, when the driver lets go of the brake during cranking. The PCM then enters a fail-safe mode with limited engine speed, and new PCM software cures the false detection. Mercedes-Benz lists U044287 with U014687 when a software conflict in the 48 V battery switches on the check engine light (LI54.21-P-078926). Expect the MIL and, depending on design, reduced power.
U0442 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor0.5 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0442
- Check engine light on
- Fail-safe mode with limited engine speed or lack of power
- Transmission codes stored alongside engine codes
Common causes of U0442
- Most likelyControl logic in the engine or powertrain software too sensitive, update available
- PossibleSoftware levels of sending and receiving units do not match after an update
- Less likelyBus wiring, connector or supply fault at the second powertrain controller
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
ECM PCM bCAN bus wiring
What each part of U0442 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 42 | The exact fault in that area. |
What to do next
- Note U0442 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 U0442
What does U0442 mean?
U0442 means "Invalid Data Received From ECM/PCM B". ECM/PCM B stands for a second engine or powertrain controller where a car carries more than one such unit; U0442 means its frames reach a receiver with invalid content, while U0115 means they stop arriving. It is a generic code, so it means the same on every make.
Is it safe to drive with U0442?
Drive gently and only to a workshop. With U0442 the car can go into limp mode (reduced power) to protect itself.
Will U0442 fail an emissions test?
Yes, it can. U0442 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is U0442 to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 2.5 hours of work. This is a job for a workshop.
Will U0442 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.