Severity: High
Can damage expensive parts or affect drivability. Limit driving and book promptly.
What U0100 means
Another module lost communication with the engine computer. Check the network and the engine computer's power and ground.
Symptoms
- No start
- Multiple warning lights
- Gauges drop out
Common causes
Most likely first
- 1Engine computer lost power or ground
- 2Damaged CAN wiring or connector
- 3Failed module on the network pulling the bus down
- 4Low battery voltage
How we diagnose it
- Check CAN bus resistance (about 60 ohms between pins 6 and 14 with key off)
- Check engine computer powers and grounds
- Unplug modules one at a time to find a shorted node
Every vehicle sets codes under its own conditions. We check the factory diagnostic steps and service bulletins for your VIN, so the repair targets the actual cause.