Circuit/System Description

There are 2 ignition 1 voltage circuits supplied to the engine control module (ECM). The first ignition 1 voltage circuit is provided by the powertrain relay, through the TAC fuse, located in the underhood fuse block. This ignition 1 voltage circuit supplies power to all the internal ECM circuits associated with the throttle actuator control (TAC) operation, and to both TAC motor control circuits to the throttle body. The ignition switch provides the second ignition 1 voltage circuit to the ECM, through the ECM 1 fuse located in the underhood fuse block. This ignition 1 voltage provides power to all internal ECM circuits, except those associated with TAC operation. The ECM continuously monitors both ignition 1 voltage circuits. If the ECM detects a voltage level difference between the two circuits, DTC P1682 will set.