OBD-II Trouble Codes

U0100 Code: Lost Communication with ECM/PCM “A”

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Your vehicle’s communication data bus serves as the line of communication between different modules in your vehicle, including its primary computer or powertrain control module (PCM). Without this line of communication, the different modules in your vehicle would not be able to send signals to one another. U0100 is among the generic trouble codes related to network communication issues.

engine control module 3
our vehicle’s communication data bus serves as the line of communication between different modules in your vehicle, including its primary computer or powertrain control module (PCM).

What Does the U0100 Code Mean?

Diagnostic trouble code (DTC) U0100 stands for “Lost Communication with ECM/PCM ‘A.’” It is triggered once there is a loss of communication between your PCM and a particular module. Once this happens, the vehicle may shut off and it may not restart unless you address the issue triggering the code.

Note that the exact definition of trouble code U0100 may vary based on the vehicle manufacturer.

CAN Bus

Your PCM communicates to other modules in your vehicle via a data bus. On many vehicles, the modules use a protocol called controller area network (CAN) to talk to one another. So, the bus is known as the CAN bus.

Basically, it works just like your body’s nervous system. Your CAN bus system is wired throughout your vehicle. Without it, the different modules in your vehicle such as the PCM, transmission control module (TCM), anti-lock braking system (ABS), or body control module (BCM) won’t be able to communicate with one another.

What are the Possible Causes of the U0100 Code?

Code U0100 is a serious trouble code that should be addressed immediately. Here are the possible triggers related to the code:

What are the Common Symptoms of the U0100 Code?

The most common symptom of this code is the “Check Engine Light.” There is also a very high possibility that your vehicle will not be able to start at all. Once this happens, it is recommended to have your vehicle checked right away for proper diagnosis.

abs control module of brake system
Your CAN bus system is wired throughout your vehicle. Without it, the different modules in your vehicle such as the PCM, transmission control module (TCM), anti-lock braking system (ABS), or body control module (BCM) won’t be able to communicate with one another.

How to Diagnose the U0100 Code

Again, U0100 is a very serious issue. To diagnose this code properly, you need to pinpoint what module and what part of the CAN bus is causing the problem. If you’re not confident about your automotive repair skills, it is best to leave the job to a professional.

However, if you’re confident about your DIY auto repair skills, here are videos you can watch to help you learn more about the troubleshooting process:

How to Fix the U0100 Code

U0100 is a generic trouble code, which means it can be seen in various makes and models. However, take note that there is no universal fix for the code. This means that the exact fix will still depend on your vehicle’s make and model. For example, repair steps for a U0100 in Honda may be different from a U0100 in a Ford vehicle.

If you’re unsure about anything, it is best to bring your vehicle or have it towed to your trusted auto repair shop. If you’re confident you can fix it yourself, you can use online auto repair resources and guides to determine what solution applies to your vehicle’s specific make and model. You can also consider getting an ALLDATA single-vehicle subscription.

Lastly, don’t forget to check your vehicle’s manual before doing any repairs.

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