Circuit/System Description

When the ignition switch is placed in the START position, a discrete signal is supplied to the body control module (BCM) notifying it that the ignition is in the START position. The BCM then sends a 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 volts to the control circuit of the PCM CNTRL relay. When this occurs, battery voltage is supplied through the switch of the PCM CNTRL relay to the terminal A X1 of the starter solenoid. The ECM always supplies some voltage to the control circuit of the PCM CNTRL relay, through a pull-up resistor. If the circuit becomes open or shorted, then the ECM will set DTCs.