U0100
CriticalU0100 — Lost Communication With Engine Control Module Over CAN Bus
Description
What This Code Means
Code U0100 indicates a loss of communication between the engine control module (ECM/PCM) and other modules over the CAN bus. The ECM is the main computer that manages engine operation, so a communication breakdown can cause serious handling problems. A faulty ECM, damaged wiring, or CAN bus issues can all trigger it.
Symptoms
Symptoms
- Check Engine light is on
- Engine may not start or may run rough
- Loss of power
- Transmission shifting problems
- Diagnostic equipment can't connect to the ECM
Causes and fixes
Diagnosis and Repair
- Check ECM power and ground.
- Check the CAN bus wiring for a short or open circuit.
- Inspect the ECM connectors for corrosion or damage.
- Use ISTA to run a network test.
- If the ECM is faulty, replace it and program it with the correct software.
Possible secondary damage
Secondary Problems
Prolonged loss of communication can leave the car completely inoperable. Other modules may also log faults from the missing data, triggering cascading failures. In some cases the ECM will need replacement and programming, which is an expensive repair.