U0401 code meaning
Invalid Data Received From ECM/PCM A
Network system Generic code U04xx codes Check engine light
What U0401 means
U0401 is stored by a module that keeps receiving the engine or powertrain controller's messages but finds their content faulty. Most often the transmission controller logs it; Ford's 2012 OBD summary names engine torque and pedal position as the data concerned. In GM's 2025 tables the TCM checks rolling counter, protection value and checksum of several ECM frames, treats 8 bad results within 18 checks as a failure and classes the code Type A (MIL at once); GM's driver-assist module sets it as Type C and only switches off adaptive cruise. Saab's 2011 code list adds sub-codes 72 (counter) and 74 (checksum). Bentley's Continental GT gearbox stores U040100 when brake pressure decays too fast in ACC stops; a passive entry can stay. Ford's 2020 Escape and GM's 2024 Corvette needed new software. U0100 means lost contact.
U0401 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0401
- Check engine light, often stored in the transmission controller
- Harsh shifts or transmission limp-home mode
- Adaptive cruise control switched off
Common causes of U0401
- Most likelySoftware of the ECM/PCM or of the receiving module (update available)
- PossibleECM sends a signal flagged invalid, for example after its own sensor fault
- PossibleDisturbed CAN traffic from connectors, wiring or low battery voltage
- Less likelyEngine control module internally faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
ECMCAN bus wiring
What each part of U0401 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 01 | The exact fault in that area. |
What to do next
- Note U0401 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 U0401
What does U0401 mean?
U0401 means "Invalid Data Received From ECM/PCM A". U0401 is stored by a module that keeps receiving the engine or powertrain controller's messages but finds their content faulty. It is a generic code, so it means the same on every make.
Is it safe to drive with U0401?
Drive gently and only to a workshop. With U0401 the car can go into limp mode (reduced power) to protect itself.
Will U0401 fail an emissions test?
Yes, it can. U0401 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 U0401 to fix?
Difficulty: hard. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will U0401 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.