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P2509 Powertrain

ECM/PCM Power Input Signal Intermittent

The ECU detects sporadic interruptions of its supply voltage. The fault is set when supply drops below a threshold for short periods, often during cranking or due to a poor connection.

Affected components

  • Ecu power supply
  • Main relay
  • Battery terminals

Common causes

  • High likelihood: Poor battery cable connection
  • Medium likelihood: Intermittent main relay
  • Low likelihood: Connector with intermittent contact under vibration

Diagnostic notes

  • The malfunction indicator lamp may illuminate

Sources

Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.

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