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ElectricalSeverity High: diagnose before driving on

P0686ECM/PCM Power Relay Control Circuit Low

What it means

The main relay control circuit reads too low a voltage.

Symptoms

  • No start or stalling

Common causes

  • Control wire shorted to ground
  • Faulty relay

What to check first

  1. Check the control wire
  2. Test the relay
  3. Check ECU supplies
Can I drive with P0686? Not recommended. P0686 can lead to stalling, limp mode or engine damage; diagnose it before driving further.

Generic OBD-II meaning. Manufacturer-specific meanings and checks can differ; always check the service information for the car.

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P0686: questions and answers

What does P0686 mean?

P0686: ECM/PCM Power Relay Control Circuit Low. The main relay control circuit reads too low a voltage.

What are the symptoms of P0686?

No start or stalling.

What causes P0686?

Control wire shorted to ground. Faulty relay.

How do you diagnose P0686?

1. Check the control wire 2. Test the relay 3. Check ECU supplies

Can I drive with P0686?

Not recommended. P0686 can lead to stalling, limp mode or engine damage; diagnose it before driving further.