U0100
Lost Communication With ECM/PCM A
Network · Generic (all makes)System: Network/Communication + Electrical/Circuits
Stop driving. Risk of damage or a breakdown.
Likely causes
- Weak battery or bad ground
- Damaged wiring or connector on the network
- Failed engine computer (ECM/PCM)
What to check first
Other modules can't hear the engine computer. Check battery voltage and grounds first: low voltage causes many communication codes.
Typical repair cost
$100 – $1,200
Independent-shop parts and labor for the usual fix. Your price depends on the actual cause and the vehicle.
Next step
General information, not a diagnosis of your vehicle. Repair costs are typical shop ranges, not quotes.