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P0685
Systeem
Powertrain (Electrical)
Scanner vereist
Full-system scanner (engine, ABS, SRS, transmission, service resets)

ECM/PCM Power Relay Control Circuit Open

Understand P0685, common causes, and the right TOPDON scanner to diagnose it.

Main ECM power relay control circuit open — engine may not start or stall.

Veelvoorkomende symptomen

  • No-start
  • Stalling
  • Intermittent crank no-start

Typische oorzaken

  • Failed ECM relay
  • Open relay control wire
  • Blown fuse
  • ECM internal driver fault

Welke scanner heb je nodig?

Full-system scanner (engine, ABS, SRS, transmission, service resets)

Gebruik live data en freeze frame voordat je onderdelen vervangt. ABS-, SRS- en U-codes vereisen meestal een full-system scanner.

Diagnosetips

  • Leg freeze frame vast wanneer de code voor het eerst verschijnt
  • Wis de code pas na het oplossen van de oorzaak
  • Controleer op gerelateerde pending codes
  • Controleer of accuspanning boven 12,4 V is voordat je sensoren suspecteert

Aanbevolen TOPDON scanners

Veelgestelde vragen

What does P0685 mean?
P0685 indicates ecm/pcm power relay control circuit open. Main ECM power relay control circuit open — engine may not start or stall.
Can I diagnose P0685 with a basic code reader?
P0685 may set in the engine module, but related diagnostics often benefit from an enhanced or full-system scanner with live data and freeze frame.
Which TOPDON scanner do I need for P0685?
Full-system scanner (engine, ABS, SRS, transmission, service resets) See recommended tools on this page.
Is it safe to drive with P0685?
It depends on the code and symptoms. Flashing check engine lights and misfire codes should be addressed immediately. Consult a professional if unsure.