Error code

OBD2 U0100

OBD2U0100
Diagnostic Trouble Code· Standard OBD-II fault code read from the vehicle's onboard diagnostics.

What it means

Lost Communication With ECM/PCM A.

Severity

highDrive cautiously and seek repair immediately.

Summary

U0100 indicates lost communication between the engine control module (ECM) and other vehicle modules on the CAN bus network.

Symptoms

  • Malfunction Indicator Light (MIL) is on
  • Lack of power
  • Poor fuel economy
  • All engine-related indicators and gauges are inoperative

Common Causes

  • Open circuit in the power supply to the ECM
  • Open circuit in the ground supply to the ECM
  • Open circuit in the CAN bus + or - lines
  • Faulty ECM (rare)

Diagnosis

  1. Check for technical service bulletins related to your vehicle.
  2. Inspect fuses and grounds for the ECM/PCM.
  3. Use a digital multimeter to check CAN bus resistance between specific terminals.
  4. Visually inspect CAN bus connectors and wiring for damage or corrosion.

Fixes

  • Repair open circuits in power supply, ground supply, or CAN bus lines.

FAQ

What should I do if my MIL light is on and I have a U0100 code?

Check fuses and grounds for the ECM/PCM. If issues persist, consult a professional mechanic.

Is it safe to drive with a U0100 code?

Drive cautiously as communication issues can affect vehicle performance and safety.

View source

Not affiliated with OBD2. Answer summarized from the manufacturer's manual linked above; consult that source for the authoritative procedure.

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