Trouble codes › U0100

U0100 Lost Communication With ECM/PCM "A"

Network

U0100 means other modules have lost communication with the engine computer, often from low voltage, a blown fuse or a wiring fault.

Another module on the vehicle's network (for example the transmission or ABS module) stopped hearing from the engine computer. The problem is in the communication path, the engine computer's power, or the computer itself.

Can I keep driving? Yes, but get it fixed soon.

The vehicle may stall, not start, or show many warning lights. Get it checked before relying on it.

Common causes

  1. Low battery voltage or a loose battery connection
  2. A blown fuse or bad ground to the engine computer
  3. Damaged network (CAN) wiring or a corroded connector
  4. A failing engine computer

Symptoms

  • Many warning lights at once
  • Gauges dropping out
  • Stalling or no start

What to check first

  1. Check battery voltage and clean, tight battery terminals.
  2. Check the engine computer's fuses and grounds.
  3. Look for water in connectors and chafed wiring near the engine computer.
  4. A shop can check the network wiring with a meter or scope if power and grounds are good.

What does U0100 mean on your vehicle?

The likely cause depends on your engine. iRepair researches your exact year, make, model and engine (service bulletins, recalls and owner reports) and tells you what to check first. Your first 3 questions are free.

Ask iRepair about U0100

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Related codes

General guidance for U0100 on most vehicles. Some makers use the same code a little differently; confirm in the service information for your vehicle, put safety first, and see a professional when in doubt.