The diagnostic trouble code U0401 stands for “Invalid Data Received from ECM / PCM.

U0401 does not specify a concern in the vehicle’s components but rather indicates a miscommunication from the Powertrain Control Module. The PCM ensures smooth communication between different modules. The “U” in the trouble code “U0401” stands for an issue in the data network. Data Network, or Controller Area Network, is what modern vehicles use for different control modules to communicate.

When indecipherable data is received from other modules and their communication cannot be specified by the PCM, the trouble code “U0401” will be set.

Why am I getting code U0401?

There could be various reasons you may be getting this trouble code, but the primary one concerns a miscommunication between modules. Let’s look at other possible reasons you could be seeing this code on your dashboard:

If your vehicle has malfunctioning sensors and transmits invalid data to your PCM, this trouble code is triggered.

If the vehicle’s control units, such as ECM/PCM, are faulty and cannot decode the transmitted data from the sensors, it’s most likely that your PCM will display the code U0401.

The vehicle’s ECM or PCM could also be wired wrong electrically.

Another problem could be with the data network. Problems could also be with your battery or charging system, causing abnormal system voltages.

How do I fix code U0401?

Step #1: Diagnosis

The best way to start fixing the code is by diagnosing it correctly and determining the specific problem with your vehicle. Several common issues could exist, but those are just speculations until diagnosed.

Start by using the correct scanning tool to scan the DTC. While scanning, ensure you study the freeze frame data to confirm the parameters and data responsible for the code. Next, check if there’s any damage to the wiring harness with your ECM or PCM. The most crucial aspect of diagnosing is ensuring the communication circuits between modules are working correctly. Other than providing a satisfactory working of your modules, you can also try resetting the code and giving your car a test drive. If the code reappears, it’s time to take it to a mechanic.

Step #2: Fix

It is essential to assess the system’s voltages to reach a possible fix to ensure they are working as intended. If that looks in order, one may need to repair or replace the Engine/Powertrain Control Module if it is not receiving necessary power or ground signals.

Further examination should involve searching for any additional codes linked to this issue so all associated problems can be solved at once. If all of these methods prove futile, seeking professional help would be the best option.


  1. Is PCM the same as ECM?

    With the advent of ever-advancing engine control systems, confusion between two similar component names is quite common. Powertrain Control Module (PCM) and Engine Control Module (ECM) are often used interchangeably, but there are distinct differences that should be noted.

    The PCM is functionally defined as responsible for controlling the entire powertrain system, whereas the ECMs are primarily concerned with directing and managing fuel delivery, ignition timing, and other functions within the engine itself.

    In short, the ECM controls various components of the engine. At the same time, the PCM incorporates signals from various sensors to control multiple systems together in a vehicle, making it a more capable component than an ECM.

  2. What causes no communication with ECM?

    Communication between the Electronic Control Module (ECM) and vehicle systems can be interrupted for various reasons. The most common cause of no contact with ECM is related to the power and ground; either one or both are unavailable to the ECM as it needs stable voltage over a certain threshold for communication to occur.

    Low battery voltage could also cause communication issues if the power is insufficiently supplied to the ECM. Wiring connection problems such as corroded connectors, disconnected grounds, faulty wiring, and knocked loose contacts can all result in poor conductivity between components at different points in the circuit, which would prevent a successful data transmission.

    Finally, an internal fault within the ECM itself may prevent it from communicating correctly with other modules.

  3. How do I reset my ECU engine control unit?

    Generally speaking, resetting the ECU involves disconnecting the battery and then pressing and holding the accelerator pedal all the way to the floor for several seconds. Afterward, reconnect the battery and start your engine – it’s essential to ensure that all check lights illuminate as usual during this process.

    You should also observe an immediate increase in idle speed after resetting your ECU; if this doesn’t happen, it’s likely to further investigation is needed.

Conclusion: U0401 At a Glance

U0401 is an automotive code that stands for Invalid Data Received from ECM/PCM. This error code is generated when there is a problem with the communication between the engine control module (ECM) and the powertrain control module (PCM).

Typically, the problem is caused by a bad ground connection, a faulty wiring harness, or a defective sensor. If you experience this error code, it is essential to do your due diligence and have your vehicle inspected by a qualified technician as soon as possible if all fails.

If this article on DTC U0401 helped you, check out our DTC page to learn more about other trouble codes.