Error code · Communication between control units

U0001 — High Speed CAN Communication Bus

Don’t put off the repair

A fault code doesn’t yet mean the unit or sensor itself is faulty: often it’s the plug and connector leading to it.

Possible causes

What you can do yourself

  1. Check the battery and terminals: at low voltage control units lose communication.
  2. Check this control unit’s fuses.

Stop and don’t drive on if:

  • The instrument panel went dark or many warning lights came on at once
  • Power steering is gone or the brakes don’t work as usual
OOleg’s tip: check the connector

Often the cause is simple — there is no contact in the connector (plug). Look at the connector from the back: remove the rubber seal and you will see whether a wire is corroded or has come off completely. Corrosion shows up as green deposits. Ideally, gently pull each wire towards you one at a time: a sound wire stays in place, while a corroded one simply comes off — it needs to be repaired.

Unplug and inspect connectors with the ignition off.

On Oleg’s website:Car wiring repair ↗

The explanation comes from the error code reference in the AvtoElektrik PRO app.

Need a mechanic’s help?

Couldn’t fix it yourself? Oleg, an auto electrician, does computer diagnostics and repairs: he comes out anywhere in Almaty or sees you at his workshop.

Want to figure it out yourself?

Oleg’s course “Car computer diagnostics with a scan tool”: how to hook up a scanner, read codes and live data, and use them to find the cause. The first lessons are free.

Scan tool diagnostics course →

Nearby codes

All codes in U00xx →

Who keeps this reference

The reference is kept by Oleg Dmitriev, an auto electrician from Almaty with 26 years of experience: computer diagnostics of cars and trucks, repair of control units (ECUs). Can’t find the cause? Message him.