U0401

Invalid Data Received From ECM/PCM A

Network / communication Generic OBD-II High

What it means

U0401 means another module is receiving data from the engine/powertrain control module (ECM/PCM) that is out of range or implausible. Because so many systems depend on engine data, this can trigger limp mode, rough running, stalling, or a no-start. Treat it as serious: check the ECM/PCM's power, grounds, and wiring, and drive as little as possible until it's fixed.

High

Can I keep driving? Maybe not — the engine controller is sending implausible data, so the car can drop into limp mode, run poorly, stall, or fail to start; drive minimally until fixed.

Real-world scan data

Seen in

2,571

scans in the past year

Found in

0.4%

of scans

0.7%

of scans that found faults

Appears alongside · share of U0401 scans

U3003in 27.9% of scans

U0100in 21.1% of scans

C0034in 15.8% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Reduced-power or limp mode
Rough running, stalling, or a hard/no-start condition
Warning lights on across several systems
Other modules storing 'lost communication' or 'invalid data' codes for the ECM/PCM

Common causes

Most likely first

ECM/PCM broadcasting out-of-range or implausible values onto the CAN busLikely
Internal ECM/PCM fault or corrupted softwareCommon
Wiring, connector, or ground fault at the ECM/PCM corrupting bus dataCommon
Power-supply problem to the ECM/PCM (low or unstable voltage)Less often

How to diagnose & fix

Work through it in order

Scan all modules and record every stored code, including companion communication codes.
Check ECM/PCM power and grounds and the battery/charging voltage first.
Inspect ECM/PCM wiring and connectors for damage, corrosion, or backed-out pins.
Verify ECM/PCM software is correct; reflash or, if internally failed, replace and program, then clear and re-test.

FAQ

Quick answers

Is it safe to drive with U0401?+

Not really. The engine controller is sending bad data, which can cause limp mode, stalling, or a no-start. Drive as little as possible and get it diagnosed quickly.

Can I just clear U0401?+

It will return, often quickly, because the ECM/PCM is still reporting invalid data. The underlying wiring, power, or module fault has to be repaired.

Read & clear U0401 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX