U0020 Code: Low Speed CAN Communication Bus Performance

The controller area network (CAN) is a data bus that lets various systems like electronic steering, climate control, anti-lock braking, and lighting controls, among others, communicate with one another.

The CAN protocol was approved by the Environmental Protection Agency (EPA) for 2003 and newer vehicles. It was proposed as a legal requirement for all vehicles by 2008.

What Does the U0020 Code Mean?

Diagnostic trouble code (DTC) U0020 stands for “Low Speed CAN Communication Bus Performance.”

The CAN bus is a central network that lets all modules see the messages being sent by different modules. While this might be the case, the messages being transmitted have their respective identifiers that only let the affected module act on the data received.

There are three CAN classifications according to speed rating with Class A as the lowest and Class C as the highest classification.

The CAN bus is subject to an electrical fault, which can affect the performance of other systems. If a problem with the low-speed CAN bus occurs, on-board diagnostics (OBD-II) will log a U0020 trouble code.

Note: The definition of code U0020 might be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of the U0020 Code?

• Network problems
• Low voltage condition
• Faulty control module
• Wiring issues, such as a damaged wire or poor connection

What are the Common Symptoms of the U0020 Code?

• Illuminated check engine light
• Various problems with the electronics and computer controls

How to Diagnose the U0020 Code

Trouble code U0020 is a generic powertrain code that can be logged in vehicles with an OBD-II system. However, steps for diagnosis can vary, depending on vehicle specifications. Diagnosing a trouble code might require you to use a scan tool and inspect the vehicle for damaged or corroded wiring, among others.

If you’re not used to doing this task on your own, you can always seek the help of a certified mechanic to do the job for you. Otherwise, you can go ahead and diagnose the problem on your own.

How to Fix the U0020 Code

Without the right tools and technical knowledge, attempting to fix a U0020 code can be tricky and might even lead to further complications if done incorrectly. Under these circumstances, it’s best to bring your vehicle to the nearest repair shop and have a trained professional perform the necessary repairs.

But if you think you have enough DIY skills to do the job yourself, make sure to have the right equipment and information before proceeding. Trouble codes don’t have a universal solution that will work for all makes and models, which is why it’s important to consult the right manuals. Guides like those from Chilton or an ALLDATA subscription contain vehicle-specific repair information, so you might want to check those out before you proceed.