Key-P function - GF27.10-P-3028AHO

TRANSMISSION 724.2 in MODEL 212 

Key-P function requirements, general 

• Vehicle speed < 8 km/h

Key-P, general 

The designation "Key-P" comprises all the functions, which in addition to the parking brake, help to secure the vehicle to prevent it from rolling away unintentionally.

If the ignition key is turned to position "0" (circuit 15 C) and removed while the vehicle is driving or rolling, the transmission is automatically shifted to gear range "N". As a result, the vehicle can roll "freely".

Key-P function sequence 

The function sequence is described in the following steps:

• Park pawl function sequence 
• Function sequence for locking in gear range "P" 
• Emergency-P function sequence (see document, Emergency-P Function) 

Function sequence for park pawl in vehicles up to facelift 13 

The fully integrated transmission control unit (Y3/8n4) only permits a shift to gear range "P" over the DIRECT SELECT lever (S16/13) when the transmitter key (A8/1) is turned to the "circuit 15 ON" position, and the brake pedal is operated.

The "circuit 15 ON" signal is sent by the electronic ignition lock control unit (N73) over the chassis CAN (CAN E) to the CDI control unit (N3/9) or the ME-SFI [ME] control unit (N3/10). This routes the signal over the drive train CAN (CAN C) to the fully integrated transmission control unit.

In order to ensure that after parking the vehicle, the gear range "P" is active, the transmitter key can only be removed from the electronic ignition lock control unit when in this position.

The vehicle is secured mechanically by blocking the park pawl gear in the transmission.

With code (889) Keyless-Go

For vehicles with code (889) Keyless Go, a shift is made to gear range "P" when the driver opens the driver door after switching off the engine.

The left front door control unit (N69/1) sends the status over the interior CAN (CAN B) to the front SAM control unit with fuse and relay module (N10/1). This routes the status over the chassis CAN to the CDI control unit or to the ME-SFI [ME] control unit. The CDI control unit or the ME-SFI [ME] control unit sends the information over the drive train CAN to the fully integrated transmission control unit.

As of facelift 13 the existing chassis CAN is replaced with chassis-CAN1 (CAN E1). An additional chassis-CAN2 (CAN E2) is used between the instrument cluster (A1) and the front SAM control unit with fuse and relay module. The ME-SFI [ME] control unit or the CDI control unit is the interface between the drive train CAN and chassis-CAN1. The interface between chassis-CAN1 and chassis-CAN2 is formed by the front SAM control unit with fuse and relay module.

Function sequence for locking in gear range "P" 

Gear range "P" remains active if the following conditions are fulfilled:

• No power supply of the fully integrated transmission control unit
• No enable signal from drive authorization system stage 3 (DAS 3)
• Brake pedal not actuated