U0401

Invalid Data Received From ECM/PCM "A"

Car Fault Codes Network

Can you still drive? With care, short trips only

Who can fix it? Needs a workshop

Typical repair time 1 hour – 5 hours

Typical cost SAR 150 to 5,000

What it means

Another module, such as the transmission module (TCM) or the ABS module, is receiving messages from the engine computer (ECU) over the network, but their content is implausible or invalid. Communication exists, and the problem is usually in the engine computer or a sensor it relies on, so its codes are read first.

Symptoms4

Check engine or other warning lights on.
Transmission in limp mode or abnormal shifting.
Cruise control or stability control disabled on some vehicles.
Incorrect cluster readings such as temperature or the tachometer.

Possible causes5

A faulty sensor whose value the engine computer shares with other modules, such as the accelerator pedal or temperature sensor, with its own code stored in the engine computer.
Incorrect programming or coding of the engine computer after replacement or an update.
Low battery voltage or weak charging.
Intermittent network wiring or connector fault that corrupts messages.
Internal engine computer failure.

How to diagnose5

Read the engine computer codes first and fix any sensor or internal fault codes there.
Note which module stored the code, since it shows what kind of data is being rejected.
Measure battery and charging voltage with the engine running.
Check whether the engine computer was replaced or updated recently, and compare its software version with the manufacturer specification.
Inspect network connectors and measure line resistance, especially if the code is intermittent.

How to fix6

Repair the sensor or circuit stored in the engine computer.
Charge or replace the battery and fix any charging problem.
Reprogram or recode the engine computer with the correct version.
Repair damaged network connectors or wiring.
Replace and program the engine computer if an internal fault is proven.
Clear codes in all modules and confirm the code does not return.

Repair cost

0–500

500–2,000

2,000–5,000

5,000+

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost is low for a sensor, battery or software update, and reaches the upper end if the engine computer must be replaced and programmed.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026

Frequently asked questions

What is the difference between this code and U0100?

U0100 means the engine computer's messages are not arriving at all. This code means they arrive but the content is invalid, so diagnosis starts with the engine computer's codes and sensors.

Does the engine computer need replacing?

Rarely. Most cases come from a faulty sensor, incorrect programming or low voltage, and the computer is replaced only after those are ruled out.

This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.

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