D Group 28 Design and Function MID 223 Gear Selector Control Unit The “Premium Tech Tool” (PTT) is the preferred tool for performing diagnostic work. Contact your local dealer for more information. System Overview The gear selector is attached to the drivers seat and can be folded away to aid in entering the cabin. There are two available selector configurations, a basic and a premium. The selector in the vehicle is dependant on which program package level the vehicle is built with. Both selectors have gear positions of R (Reverse), N (Neutral), D (Drive), and M (Manual).
With the selector in the drive position the transmission will shift as an automatic, performing gear selections and shifting without driver input. When in the manual position, the driver either selects the gears using the gear selector button (premium selector) or will lock the gear that the transmission is presently operating in and hold that gear until the selector is placed in the drive position again (basic selector). With the basic selector, if the manual position is engaged at a stop the vehicle will start in first and hold that gear. The basic selector isn’t equipped with a gear selector button or a economy/performance dive mode button.
In situations where the I-Shift is unintentionally left in gear with the parking brake applied, the TECU will automatically go to neutral when the key switch is turned off. This is done to avoid the transmission getting stuck in gear due to drive line "torque up". There is a gear selector electronic control unit (GSECU) that is located in the center of the dash. The GSECU receives signals from the selector and interprets these signals into communication information that is transmitted to the TECU.
Selector Folding The gear selector is capable of folding forward to aid in cab entry and is also used to identify which software level that is programmed in the Transmission Electronic Control Unit (TECU). With the selector in the neutral position (N) press in the fold button and the lever can be folded forward. The display will then show the program package level in place of the driving mode. This is found just to the right of the present gear within the display. Limp Home Mode Note: Limp Home Mode should only be used to get a vehicle to a safe or secure location. It is not meant for driving any distance. driving mode in the DID.
In "Limp Home Mode", only forward gears 1, 3 and 5 are available for vehicles with the premium selector and only first gear for vehicles with the basic selector. No matter which selector the vehicle has, reverse gear 1 is available also. The vehicle must be stationary to shift gears. The "Limp Home Mode", will be deactivated when the ignition is turned off. This mode is only meant to get a vehicle to a safe or secure location. At times when a sensor failure or certain internal transmission damage has occurred, "Limp Home Mode" can be activated. Press the ”L” button on the gear selector and move the gear lever to the D position to active "Limp Home Mode".
When activated, L is displayed as the Sensors Gear Selector Electronic Control Unit The gear selector communicates with the Gear Selector Electronic Control Unit using 8 wires. These wires are used to decode a switch matrix inside the GSECU. Inside the gear selector lever there are a number of switches. Some of the switches are normal and some are hall-effect switches. The Gear Selector Electronic Control Unit is located in the center of the dash just rear of the VECU. 11