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Car encyclopedia

Engine Control Unit

The engine control unit (ECU) (or powertrain control module) is a powerful computer that manages the engine’s ignition, fuel injection, and emission systems. In some vehicles, it may also control the operation of the automatic transmission and the anti-lock brake system.

Symptoms of Wear or Failure

  • Check Engine Light illuminates with codes that cannot be repaired
  • Several unrelated trouble codes are set simultaneously
  • Vehicle may not start or run
  • Poor engine performance
  • Engine stalls while driving

Related Repair Advice

  • Many vehicles have upgradeable software in their engine control units, so be sure to check for any Technical Service Bulletins (TSBs) that pertain to possible problems
  • When replacement is required, use a new factory ECU and install the latest software
  • An ECU can be mistakenly replaced when there was actually a defective engine sensor that was accidentally overlooked in the initial diagnosis

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