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U0100 on BMW — Lost Communication With ECM/PCM

BMW

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1 source
  • Official data (NHTSA)official_feed

What U0100 means

Avoid long trips

Lost communication with the engine control module. On BMW this is often a cranking voltage dip, corroded ground points, or a communication fault between control modules (including the immobilizer).

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General information, not a diagnosis or repair instruction. Always confirm with a qualified mechanic for your specific vehicle.

Common causes

  • Damaged CAN bus wiring

Symptoms

  • Повышенный расход топлива
  • Erratic behavior across several systems at once
  • Multiple warning lights at once

What to check first

  1. Check battery voltage and ground points
  2. Verify CAN bus integrity between DME and CAS
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