Theory Of Operation

The brake switch signal must be active before the shift lever can be moved out of the park position. The Shifter Lever Assembly (SLA) Electronic Shift Module (ESM) receives two brake switch signals. The first signal is a CAN C Bus message sent to the shifter lever assembly. The second signal is a hard wired brake switch signal to the shifter lever assembly from the BCM. The CAN C Bus message is the primary brake switch signal and the hard wired signal serves as the backup brake switch signal. These two brake switch signals are compared against each other to verify proper brake switch operation.