U0401: Invalid data received from ECM/PCM A
What the code tells you on its own
- System
- Network
- Functional group
- Bus communication
- Failure type byte, when the tool sends one
- 00 (No sub-type information), 68 (Event information), A0
Communication faults — a module that stopped answering on the CAN bus, or sent implausible data. Often a symptom of a power or wiring problem rather than a failed module.
Scan tools report the same fault as U0401 and as U0401xx, where xx is a sub-type. They are one fault, and whether the sub-type appears at all depends on the tool and the protocol rather than on the car.
Diagnostics
What we see when U0401 turns up
Measured across the diagnostics run through Wrenchlane, not taken from a reference table. Figures as of 2026-10-06.
- Diagnostics
- 9
- Separate workshops
- 7
- Arrived code only
- 56%
- Most common marque
- Ford (eu)
March 2026 to September 2026
Not one shop meeting it repeatedly
No symptom description entered at all
Where we have seen it most
These are counts from our own work, not a claim about how common the fault is across all vehicles. They describe what independent workshops brought to us, which is a narrower and more specific thing.
Real cases
Real cases with U0401
Diagnoses of U0401 on real cars, written up: the car, the codes it came in with, the causes ranked and what to check first.
Bus communication
Other bus communication codes
- U0100 Lost communication with ECM/PCM A
- U0416 Invalid data received from vehicle dynamics control module
- U0121 Lost communication with ABS control module
- U0167 Lost communication with immobiliser control module
- U0155 Lost communication with instrument panel cluster
- U0019 Low speed CAN communication bus
- U0103 Lost communication with gear shift module
- U0102 Lost communication with transfer case control module
FAQ
Frequently asked questions
How do I run a diagnosis?
Select the vehicle on Start, click the Diagnostic card and choose New diagnostic. Fill in the description, the error codes and the mileage, then click Analyze.
Do I have to type the codes from my scan tool?
No. Click the camera button next to Error codes and take or choose a photo of the scan tool's screen; WrenchLane reads the codes and their descriptions into the form. You can also speak them with the microphone.
Are the public fault code pages built from my diagnostics?
They use diagnostics run in WrenchLane, with no workshop, customer, registration number or VIN shown. Each fault code page shows how often the code was seen and in how many workshops.
Run U0401 against the car in front of you
Enter the code and the symptoms and get ranked probable causes for that specific vehicle, with the checks in the order worth doing them. Free account, no card.