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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1149 (Engine Controls And Fuel - 3.6L - DTC P0496 To DTC P2235) >> DTC P0685, P0686, P0687, P0689, or P0690 >> Circuit/System Description

Circuit/System Description

WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.

The engine controls (EC) ignition relay, or powertrain relay is a normally open relay. The relay switch is held in the open position by spring tension. Battery positive voltage is supplied directly to the relay coil and the switch 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. When the ECM commands the powertrain relay ON, ignition voltage is supplied to the following fuses in the underhood fuse block:

The ignition voltage that is supplied to the ECM through the ECM fuse, provides power to the internal ECM circuits associated with the throttle actuator control (TAC) operation.

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