Electronic Transmission Range Selector Description

The Electronic Transmission Range Select (ETRS) subsystem selects the transmission range (Park, Reverse, Neutral, Drive, or Manual) by means of electronic control rather than by mechanical means. The ETRS feature is controlled in the Chassis Control Module. All Electronic Transmission Range Selector and Transmission Range Control Module DTC's will set in the Chassis Control Module. The Chassis Control Module communicates via HS GMLAN, the Chassis Expansion Bus, and LIN.

When a gear is selected, the Transmission Range Control Module (TRCM) will move the transmission manual shaft into the range commanded by the ETRS. The TRCM will communicate on HS GMLAN and the Chassis Expansion Bus.

The Backup Park Lock function is electrically isolated from the TRCM, and forces the transmission manual shaft to the Park position under specified conditions. Under these conditions the vehicle is put in Latent Fault Mode, refer to Latent Fault Mode Description . The Backup Park Lock communicates with the Chassis Control Module via LIN.

The Shifter Assembly in the ETRS system has no mechanical linkage to the transmission. Instead, the shifter will provide electrical signals based on customer input to the Chassis Control Module, where the customer shift request will be determined.

ETRS Shift Lever Assembly includes:

• Shift Interlock Button - The Shift Interlock Button has two sensors which are both inputs to the Chassis Control Module.
• Park Button - The Park Button has two sensors which are both inputs to the Chassis Control Module.
• Two Dimensional Shift Lever - The shift lever is designed so any single fault at the shifter can be isolated and error corrected by the Chassis Control Module. The shift lever position is determined by 2 internal sensors that each transmit an X and Y coordinate signal. All 4 signal circuits are inputs to the Chassis Control Module.
• Transmission Shift Lever Position Indicator - LED display located on the face of the shifter. Indicates transmission actual gear position. Displays "R N P D M", which refer to Reverse, Neutral, Park, Drive, or Manual.

Transmission Range Control Module includes:

• Coupler to coupler, or lever to rod linkage interface with the transmission manual shaft.
• Backup Park Lock function (also know as Default to Park)

The vehicle is equipped with the following Electronic Transmission Range Selector Components: 

• S3 Transmission Shift Lever
• K38 Chassis Control Module
• K173 Transmission Range Control Module
• Backup Park Lock is located within the K173 Transmission Range Control Module
• P2 Transmission Shift Lever Position Indicator is located within the S3 Transmission Shift Lever
• K71 Transmission Control Module