Circuit/System Description

There are two ignition voltage circuits supplied to the engine control module (ECM). The first ignition voltage circuit is provided by the powertrain relay through a fuse. This ignition voltage circuit supplies power to all the internal ECM circuits associated with the throttle actuator control (TAC) operation. The RUN/CRNK relay provides the second ignition voltage circuit to the ECM through a fuse. This ignition voltage provides power to other internal ECM circuits, except those associated with TAC operation. The ECM continuously monitors the voltage level difference between the 2 circuits.