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U0001: High speed CAN communication bus

The car’s control units are struggling to talk to each other on the high speed CAN network. Usually a weak battery, a connector, a wire or a module.

Code U0001 at a glance
CodeU0001
SystemCommunication network
GroupU00xx, Communication buses
TypeGeneric: it means the same on every make
Can you keep driving?With care

What U0001 means

The car’s control units (engine, gearbox, ABS and others) talk to each other over a two-wire network called the CAN bus. The high speed bus carries the most important information. One unit has noticed that messages on that network are being lost or corrupted.

Most common causes

  • Weak battery or loose terminals causing voltage drops
  • A control unit connector loose, corroded or wet
  • CAN bus wires chafed, broken or shorted
  • A faulty module dragging down the network
  • Aftermarket accessory badly wired into the network (alarm, tracker, radio)

Symptoms

  • Engine and other warning lights on at once
  • Several communication codes stored
  • Instrument cluster glitching or going blank
  • Gearbox in limp mode or starting problems

Can you drive with U0001?

With care If the car starts and runs normally, you can drive carefully to a garage. If lots of warning lights come on together, ABS or power steering fail, or the engine cuts out, do not drive it.

How to check it

Check the battery first: with the engine off it should be around 12.6 volts. Note which other codes appear and in which modules, as they usually point to the part of the network with the problem.

How to read and clear U0001 with Final OBD

Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see U0001 with this same explanation and whether it’s confirmed, pending or permanent.

With Free you read this code with its short description for nothing, and clear it if the engine stores it over standard OBD. With Pro you get the full explanation, how the car was running when it was logged (revs, temperature, load) and clearing in every control unit.

Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before the ITV. It’s all in how to read and clear fault codes and in the ITV and OBD.

Similar codes

U0001 is a generic code, so it means the same on any make, for example on BMW, Ford, Mercedes-Benz, Renault, Volkswagen, Volvo. See what Final OBD does on your car in makes and models.

What does code U0001 mean?

The car’s control units (engine, gearbox, ABS and others) talk to each other over a two-wire network called the CAN bus. The high speed bus carries the most important information. One unit has noticed that messages on that network are being lost or corrupted.

Can you drive with U0001?

If the car starts and runs normally, you can drive carefully to a garage. If lots of warning lights come on together, ABS or power steering fail, or the engine cuts out, do not drive it.

How do you clear U0001?

With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, U0001 comes back.