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 Engine Control Module. All Transmission Range Selector Controls and Transmission Range Control Module DTC’s will set in the Engine Control Module. The Engine Control Module communicates via HS GMLAN and the Powertrain Expansion Bus.

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, Powertrain Expansion Bus, or LIN.

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 Engine Control Module via LIN.

The A97 Transmission Range Selector Controls in the ETRS system has no mechanical linkage to the transmission. Instead, the A97 Transmission Range Selector Controls will provide electrical signals based on customer input to the Engine Control Module, where the customer shift request will be determined.

A97 Transmission Range Selector Controls Assembly includes:

• Park Button — Park button has two internal contacts. Single push button. Normally open switch that is closed when the button is pressed. Actuation is one push.
• Reverse Button — Reverse button has three internal contacts. Single pull button. Normally open switch that is closed when the button is pressed. Actuation is one pull.
• Neutral Button — Neutral button has three internal contacts. Single push button. Normally open switch that is closed when the button is pressed. Actuation is one push.
• Drive Button — Drive button has three internal contacts. Single pull button. Normally open switch that is closed when the button is pressed. Actuation is one pull.
• Manual/Low Button — Manual/Low button has one internal contacts. Single push button. Normally open switch that is closed when the button is pressed. Actuation is one push.

K173 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:

• A97 Transmission Range Selector Controls
• K173 Transmission Range Control Module
• Backup Park Lock is located within the K173 Transmission Range Control Module
• K20 Engine Control Module
• K71 Transmission Control Module

When a gear is selected, the Transmission will shift into the range commanded by the ETRS system. The ETRS system components will communicate on HS GMLAN and Powertrain Expansion Bus.

The Backup Park Lock functionality is internal to the Transmission, and forces the transmission into Park position under specified conditions. Under these conditions the vehicle is put in Latent Fault Mode, refer to Latent Fault Mode Description.

The A97 Transmission Range Selector Controls in the ETRS system has no mechanical linkage to the transmission. Instead, the A97 Transmission Range Selector Controls will provide electrical signals based on customer input to the Engine Control Module, where the customer shift request will be determined.

A97 Transmission Range Selector Controls Assembly includes:

• Park Button — Park button has two internal contacts. Single push button. Normally open switch that is closed when the button is pressed. Actuation is one push.
• Reverse Button — Reverse button has three internal contacts. Single pull button. Normally open switch that is closed when the button is pressed. Actuation is one pull.
• Neutral Button — Neutral button has three internal contacts. Single push button. Normally open switch that is closed when the button is pressed. Actuation is one push.
• Drive Button — Drive button has three internal contacts. Single pull button. Normally open switch that is closed when the button is pressed. Actuation is one pull.
• Manual/Low Button — Manual/Low button has one internal contacts. Single push button. Normally open switch that is closed when the button is pressed. Actuation is one push.

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

• A97 Transmission Range Selector Controls
• K20 Engine Control Module
• K71 Transmission Control Module