MasterTuning Fault code dictionary (DTC)

U0100 — Lost communication with the engine control module

Severity: Serious Can you drive? With caution: limp mode possible, have it checked soon Make: All makes (OBD-II standard)
MeaningThe other control units no longer receive engine ECU messages on the CAN bus. This is a network code, not a mechanical one.
FamilyNetwork (U)

Typical symptoms

Several warning lights together
Incomplete instrument display
Engine will not start
Automatic gearbox in emergency mode

Common causes

Interrupted ECU power or earth
Blown fuse
Damaged CAN wiring
Very flat battery
Faulty ECU (last hypothesis)

What to do

Check fuses, supplies and battery voltage before suspecting the ECU: in most cases the problem is upstream and the unit itself is healthy.

Frequently asked questions

What does code U0100 mean?

Lost communication with the engine control module. The other control units no longer receive engine ECU messages on the CAN bus. This is a network code, not a mechanical one.

Can I keep driving with code U0100 active?

With caution: limp mode possible, have it checked soon

Common causes — U0100

Interrupted ECU power or earth Blown fuse Damaged CAN wiring Very flat battery Faulty ECU (last hypothesis)

How do you fix code U0100?

Check fuses, supplies and battery voltage before suspecting the ECU: in most cases the problem is upstream and the unit itself is healthy.

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Where to get it fixed

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