Question 1

What does U0100 mean?

Accepted Answer

U0100 - Lost Communication with ECM/PCM. Another module lost communication with the Engine Control Module. ECM is not responding on the CAN bus.

Question 2

What are the symptoms of U0100?

Accepted Answer

No-start, Multiple warning lights, Engine dies, Scan tool can't communicate with ECM

Question 3

What causes U0100?

Accepted Answer

ECM/PCM failure, CAN bus wiring issue, ECM fuse blown, ECM connector corrosion, Ground wire issue, Water damage to ECM

Question 4

How much does it cost to fix U0100?

Accepted Answer

Typical repair cost: $100-$2,000. Check ECM fuses first — blown fuse is free to fix. Then check ECM connector for corrosion. ECM is often in engine bay and exposed to water.

U0100 — Lost Communication with ECM/PCM

Don't guess — diagnose U0100 the right way

Common symptoms of U0100

Common causes of U0100

Repair cost & difficulty

Vehicles commonly affected

Related trouble codes