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Error Code U0401 – Symptoms, Causes and Solutions

If you have an older Chrysler, Dodge, or Jeep car, you probably use fault codes called OBD-II. Some of these codes can be very vague and difficult to figure out without the help of a professional mechanic. The code U0401 is an example of this.

Error Code U0401 Description

This code is generated when the PCM or ECM receives invalid data from the other module. This can occur if there is a short in the wiring between the modules, or a loose connector that does not make proper contact.

Reads: P0660 OBD Error Code – Intake Manifold Tuning Valve Control Circuit/Bank 1 Open

Causes of Error Code U0401

  • ECM/PCM communication circuit open
  • ECM/PCM communication circuit shorted to VREF
  • ECM/PCM communication circuit shorted to battery voltage (BATT)

Diagnosing Error Code U0401

Diagnostic steps to troubleshoot this DTC are as follows:

Step 1: Check for loose or damaged wiring at the PCM connector and ECM connector.

Step 2: Check for loose or damaged connectors on the PCM and ECM.

Step 3: Use a scan tool to read data from the PCM and ECM. Make sure there is no communication error between them, such as poor voltage signal, short circuit in the communication cable, open circuit in the communication cable, and poor contact in the connectors or plugs of the ECU/PCM or between the ECU/PCM plugs and their harnesses; check one by one if you can find the cause by fault code U0401: INVALID DATA RECEIVED FROM THE ECU/PCM (ENGINE CONTROL MODULE).

Symptoms of Error Code U0401

If you get this error, your first step should be to check the engine oil level and coolant level. If either is low or has leaked, it can cause this error code to appear.

Next, check the engine oil pressure by connecting a pressure gauge to your vehicle’s oil pressure tap on the valve cover, if applicable. Make sure the pressure gauge is correctly calibrated for use with diesel engines (if applicable).

Next, check the engine coolant temperature using a thermometer or infrared thermometer at several points around the engine block; you should see temperatures between 50 degrees C and 100 degrees C (122-212 F).

Finally, make sure there are no visible leaks anywhere in your system before proceeding to diagnose why. U0401 It could be showing up in your vehicle’s diagnostic system.

How to Fix Error Code U0401

  • Check that the PCM connector is not loose or damaged.
  • Check that the PCM connector is free of corrosion.
  • Check that the PCM connector is not damaged by short circuits.
  • Check that the PCM connector is not damaged by overheating.
  • Check that the PCM connector is not damaged by mechanical stress.


The ECM/PCM It is the electronic component in your vehicle that controls the engine and transmission. A series of sensors send data to this computer, which helps determine everything from how much fuel to inject into each cylinder (and where on that cylinder) to when your car should shift gears.

When this part malfunctions, it can cause several problems with your car, ranging from poor performance or stalling at low speeds to an engine light that comes on and needs repairs or replacement.


U0401 – Invalid data received from ECM/PCM. This code can be caused by many things, and the solution may not be direct. However, it is good to know the most common causes in order to narrow down your search for what might need to be fixed in your vehicle.

If you’re not sure where to start, take your car to a mechanic and ask for the U0401 codes; should be able to work with you to find exactly the cause of this problem.

If you want to know other articles similar to Error Code U0401 – INVALID DATA RECEIVED FROM ECM/PCM you can visit the category Fault Codes.


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