OBDII Code List

P0686 SATURN - Engine Control Module Power Relay Control Circuit Low

Repair Importance Level: 3/3
Repair Difficulty Level: 3/3   
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Possible causes

  • Weak battery
  • Low voltage while cranking
  • Faulty Engine Control Module (ECM) power relay
  • ECM power relay harness is open or shorted
  • ECM power relay circuit poor electrical connection
  • Blown ECM fuse
  • Faulty ECM

Possible symptoms

  • Engine Light ON (or Service Engine Soon Warning Light)

P0686 Saturn Description

The powertrain relay is a normally open relay. The relay armature is held in the open position by spring tension. Battery positive voltage is supplied directly to the relay coil and the armature contact at all times. The Engine Control Module (ECM) supplies the ground path to the relay coil control circuit via an internal integrated circuit called an Output Driver Module (ODM). The ODM output control is configured to operate as a low side driver for the powertrain relay. The ODM for the powertrain relay also incorporates a fault detection circuit, which is continuously monitored by the ECM. When the ECM commands the powertrain relay ON, ignition 1 voltage is supplied to the ECM, and to several additional circuits.
OBDII Code P0686 Saturn - Engine Control Module Power Relay Control Circuit Low -

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