U0401 High Generic / SAE

U0401: Invalid Data Received From Engine Control Module A

Network and Communication Invalid Data Received Emissions related

What to do

Expect a dashboard with several warnings at once, probably reduced power, and the transmission possibly stuck in one gear. That looks like several things failing together and is almost always one fault.

Nothing else has broken. The engine computer is publishing a figure other systems cannot believe, so each of them has sensibly refused to act on it — the gearbox holding one gear, stability control switching off, cruise control refusing to engage. They are protecting themselves, not failing.

Do not let the engine control module be replaced on the strength of this code. It is one of the most expensive parts on the car and normally has to be programmed to the vehicle. The fault is usually a sensor feeding it — the module is faithfully passing on a wrong reading it was given.

Ask for every other stored code to be read and fixed first. Any code naming a specific sensor is the real problem, and dealing with it normally clears this one too.

What this code means

The engine control module is broadcasting data another module cannot accept as true. See U0400 for what distinguishes this family from lost communication.

The engine module is the most-quoted module on the vehicle, and that is why this code has such wide effects. Engine speed, load, torque, throttle position, coolant temperature and fuel status are consumed by the transmission, the stability control system, the instrument cluster, the climate control and the driver assistance systems. When what it says stops being believable, several unrelated systems object at once.

The resulting picture is alarming and is one fault: a transmission in limp mode, stability control disabled, cruise control unavailable, a dashboard covered in warnings. None of those systems has failed. Each has correctly refused to act on information it cannot trust.

The torque figure deserves specific mention, because it is the value most often at the centre of this. The transmission schedules its shifts and clutch pressures around the engine's reported torque — the conversation described at P2637 — and it is the single most consequential number the engine module publishes. An implausible torque report puts the transmission into a fixed gear rather than risk shifting on a wrong figure, which is protection and is routinely misread as a gearbox fault.

Following U0400's rule, the fault is usually upstream of the engine module. A failing sensor feeding it — throttle position, pedal position, mass airflow, crankshaft position — makes the module compute and publish a value that is genuinely wrong while the module itself is working perfectly.

So the other stored codes are the diagnosis, and this one is the consequence. A P-code naming a specific sensor alongside this is almost certainly the actual fault. Reading this code alone and concluding the engine module needs replacing — an expensive part that normally requires programming — is the outcome this page exists to prevent.

Likely causes

Start here

Faulty receiving module input · specialist
Damaged data bus wiring · moderate
Corroded or loose connector · easy
Software updated on one module only · specialist

Less common

Failed power or earth supply to the module · moderate
Faulty engine control module · specialist

Symptoms

Components involved

Information, not instruction

CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.

Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.

Community experience

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What makes one worth reading:

The car — make, model, year and engine. The same fault behaves differently on each.
What you measured, not only what you replaced.
What actually fixed it — or that nothing did, which is worth knowing too.