Credov

P0685 fault code: what it means

P0685: ECM power relay control circuit open. The engine may not start or may stall.

Engine and gearbox (powertrain) · Costly if missed

Usual causes, most likely first

  1. failed main (EFI) relay
  2. blown fuse
  3. wiring or connector fault

P0685 by make

Audi

Engine computer power relay (J271) circuit open. The car may not start.

Usual causes: faulty ECU power relay (J271); damaged power wire to the ECU; blown fuse

Honda

PCM power relay control circuit malfunction. Can cause no-start or cut-outs.

Usual causes: main (PGM-FI) relay; wiring fault; PCM

Skoda

Engine computer power relay (J271) circuit open. The car may not start.

Usual causes: faulty ECU power relay (J271); damaged power wire to the ECU; blown fuse

Volkswagen

Engine computer power relay (J271) circuit open. The car may not start.

Usual causes: faulty ECU power relay (J271); damaged power wire to the ECU; blown fuse

Not sure what P0685 means on your car? Ask Credov.

Before you clear it

Write the code down or photograph the scanner first. A code that comes straight back after clearing points to a fault that is still there. A car whose codes were cleared just before you arrived may be hiding one: the scanner's readiness monitors show "not ready" for a while after codes are cleared.

Researched by Credov from manufacturer and workshop sources. A fault code points to where a fault may be; a workshop confirms it with a diagnosis. Browse all fault codes.