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.

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.

Related codes

Often seen with U0401

U0100Lost Communication With ECM/PCM "A"U0402Invalid Data Received From TCM U0301Software Incompatibility With ECM/PCM U0400Invalid Data Received

Read & clear U0401 yourself

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

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