Sök
P0685
System
Powertrain (Electrical)
Scanner som krävs
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.

Vanliga symptom

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

Typiska orsaker

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

Vilken scanner behöver du?

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

Använd live-data och freeze frame innan du byter delar. ABS-, SRS- och U-koder kräver oftast en fullsystems-scanner.

Diagnostiktips

  • Spara freeze frame när koden först sätts
  • Rensa koden först efter att orsaken är åtgärdad
  • Kontrollera relaterade väntande koder
  • Verifiera batterispänning över 12,4 V innan du misstänker sensorer

Rekommenderade TOPDON-scannrar

Vanliga frågor

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.