Question 1

What does fault code U0100 actually mean?

Accepted Answer

U0100 means the vehicle's CAN bus network has lost communication with the engine ECU (Engine Control Module). It does not necessarily mean the ECU is faulty — wiring faults, bad earth connections or a failed CAN line resistor are far more common causes and must be ruled out first.

Question 2

Can I drive my car with a U0100 code showing?

Accepted Answer

We strongly advise against it. U0100 can cause a no-start condition, sudden cut-outs at speed, or loss of critical engine management data. Driving with this fault active is a safety risk and may worsen underlying electrical damage.

Question 3

How much does diagnosing U0100 cost at MnF Motors in Enfield?

Accepted Answer

Our electrical diagnosis starts from £65 and covers a full CAN bus communication test, wiring continuity checks and earth resistance measurement. We quote transparently before any repair work begins — no hidden charges.

Question 4

Does U0100 always mean I need a new ECU?

Accepted Answer

No. In our experience, the majority of U0100 faults trace back to corroded earth points, damaged wiring looms or failed CAN bus terminators — not a faulty ECU. A new ECU is an expensive part and should only be fitted after thorough electrical testing confirms it is genuinely the cause.

Question 5

How long does the diagnosis and repair take?

Accepted Answer

Diagnosis typically takes 1–2 hours. If the fault is a wiring or earth issue we can often repair it the same day. ECU-related repairs or sourcing specialist parts may extend the turnaround, and we will always keep you informed with a clear timeline.