Circuit/System Description

When the ignition switch is placed in the start position, a discrete signal is supplied to the body control module (BCM). The BCM then sends a serial data message to the engine control module (ECM) that crank has been requested. The ECM then verifies that the transmission is in park or neutral. If it is, then the ECM then supplies 12 V to the control circuit of the STRTR relay. The ECM monitors the voltage on the control circuit, to ensure that the circuit is not open or shorted.