U0001 Code (Symptoms, Causes, and How to Fix)

While most engine lights come on randomly as various components give out, chances are if you have a code U0001 it’s because you were messing around with things under the hood. That’s not exclusively the case, but having this code just kick on randomly is extremely rare but not impossible.

But if you’re seeing a code U0001, what does it mean, how common is it, and most importantly, how do you fix it? We’ll go over all of that for you here, but any way you look at it, a code U0001 is bad news.

What Does Code U0001 Mean?

OBD-II Trouble Code U0001 Description
High Speed CAN Communication Bus

Reading that engine code description translates to a bunch of gibberish unless you already have a solid mechanical background. But essentially, the CAN-bus is a system that transfers messages and data from different control modules to the various components.

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When there’s a problem with the CAN-bus the control modules can no longer communicate with the components, and that’s what a U0001 trouble code is telling you is happening.

See Also: U0073 Code, U0100 Code, U1000 Code

Symptoms of Code U0001

check engine light

There are two main consistent problems with code U0001. First, you’ll have a check engine light. Second, when you read the check engine light you will typically get a U0001 and another code that helps point you in the direction of the specific part of the CAN-bus that isn’t working.

However, while both those things are pretty typical, if you have code U0001, you will have another performance problem. However, because there are so many different control modules and they control so many different components, it’s challenging to tell you exactly what’s going to happen.

You might not have air conditioning, you might not be able to get your vehicle to start, or you might not be able to shift gears. It all comes down to whatever control module is currently acting up.

But while the exact problem will change depending on the portion of the CAN-bus that is no longer communicating, there will be some kind of performance problem with a code U0001.

So, the common symptoms of a code U0001 are:

  • Check engine light
  • Another code
  • Tons of wide-ranging performance problems

Causes of Code U0001

PCM vs ECM vs ECU vs TCM

First off, a code U0001 is extremely rare unless you’re tinkering with the electronics of your vehicle yourself. We’re not talking about replacing sensors here, we’re talking about replacing control units or trying to rewire entire systems.

If you’re doing things like that, then a code U0001 isn’t all that common, but then you likely know what caused the problem even if you don’t know how to fix it.

However, if you haven’t been doing any of those things the two most common causes of a code U0001 are:

  • Faulty control module (ECM, TCM, BCM, etc.)
  • Faulty CAN-bus

Unfortunately, both are expensive fixes, and you’ll need to take your vehicle to a dealership so they can program all the new components to work with each other.

Is Code U0001 Serious

For the most part, yes. If you have a code U0001 something on your vehicle simply isn’t working. You might not be able to get your engine to start at all, or you might never have air conditioning again.

It all comes down to what module is having the communication issues with the CAN-bus. If it’s the air conditioning unit, then you won’t have air conditioning. If it’s the ECM, you won’t have anything.

But since this code shuts off the entire control unit, there’s no real workaround. Whatever control unit it affects won’t be able to do anything, and that’s going to shut down any component that interacts with it.

How to Fix

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While we normally like to give you some pointers on how you can fix a trouble code yourself, a U0001 isn’t one of those codes where you can figure it out. You’re either an electrical troubleshooting guru, and then you’re probably not here looking for electrical troubleshooting device, or you’re taking it to someone that is.

Even if the problem is a faulty control module, you’re still going to need to take your vehicle to a dealership so they can program the new control module to the VIN with proprietary software.

However, there is one caveat to all this. If you took your vehicle apart and installed a bunch of aftermarket components and then this code came up, and we’re mainly talking aftermarket electrical components, take it all off and put it back the way it was.

You can try to find someone to pour through schematics to try and figure it out for you, but most mechanics won’t take on the headache, and those that will are going to charge you an arm and a leg.

Adam Mann

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