Circuit/System Description
WARNING: This page is about a different car, the 2010 Chevrolet Malibu. However, it is still accessible from the selected car via links, so may be relevant.
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 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, the ECM then supplies 12 V to the control circuit of the CRNK relay. When this occurs, battery voltage is supplied through the switch of the CRNK relay to terminal A X2 of the starter solenoid. The ECM monitors the voltage on the starter relay control circuit. If the voltage is not what is expected, then DTC P0615 sets.