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 |
|---|---|
| System | Communication network |
| Group | U00xx, Communication buses |
| Type | Generic: 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.
Open the bonnetthe in-depth explanation
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 its description and whether it’s confirmed, pending or permanent.
If the engine stores it over standard OBD, with FREE you read this code with its explanation for nothing and clear it. With PRO you also read the faults of every control unit and clear them in all of them.
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 an inspection. It’s all in how to read and clear fault codes and in inspections and OBD.
Similar codes
- U0002 The high speed CAN network gives readings outside the normal range
- U0003 The high speed CAN network (high line) has a broken or disconnected wire
- U0004 The high speed CAN network (high line) gives a lower signal than normal
- U0005 The high speed CAN network (high line) gives a higher signal than normal
- U0073 Control module communication bus A off
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.
Read it on your car
Final OBD reads and clears engine faults through standard OBD for free, each one explained in plain English. With PRO it also reads the faults of every control unit, each make’s own codes included, and clears them in all of them.
