Circuit Description

Moving the ignition switch to the START position signals the body control module (BCM) through discrete inputs from the ignition transducer that engine crank has been requested. The BCM verifies that theft is not active and sends a serial data message to the engine control module (ECM) requesting engine start. The ECM receives a 12-volt signal from the park/neutral position (PNP) switch or clutch pedal start switch notifying that it is safe to start the engine. There is a splice on this circuit in the fuse block-underhood that supplies power for the CRANK Relay coil. The CRANK Relay coil control circuit is then grounded by the ECM closing the switch in the CRANK Relay, suppling 12 volts to the S-terminal of the starter. Ground is supplied through the engine block.