Circuit/System Description

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2012 GMC Yukon XL, 2012 GMC Yukon, 2012 Chevrolet Tahoe, 2012 Chevrolet Suburban, and 2012 Chevrolet Avalanche. 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 sends a serial data message to the engine control module (ECM) that crank has been requested. The ECM then verifies that the automatic transmission is in Park or Neutral, and that the immobilizer is not disabling engine starting. If conditions are acceptable for cranking, then the ECM supplies 12 V to the control circuit of the STRTR relay. When this occurs, battery voltage is supplied through the switch of the STRTR relay to terminal S X2 of the starter solenoid, and the engine cranks. The ECM monitors the voltage on the STRTR relay control circuit. If the ECM detects that the STRTR relay control circuit is open, shorted to ground, or shorted to voltage, then DTC P0615 sets.