Key-P Function - GF27.10-P-3028ANO

Transmission 725.096 in model 213 

up to model year 2021 

Key-P function requirements, general 

• Circuit 15 ON
• Brake pedal operated
• 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.

To check the function requirements, the fully integrated transmission control unit (Y3/8n4) reads in the following signals:

• The status of "Circuit 15 ON" from the electronic ignition lock control unit (N73) over the chassis FlexRay (Flex E), powertrain control unit (N127) and the drive train CAN (CAN C1).
• Service brake status from Electronic Stability Program control unit (N30/4) via chassis FlexRay, powertrain control unit and drive train CAN
• Vehicle speed signal from instrument cluster (A1) via user interface CAN (CAN HMI), electronic ignition lock control unit, chassis FlexRay, powertrain control unit and powertrain CAN

The vehicle speed is calculated using the wheel speed signals.

Key-P function sequence 

The function sequence is described in the following steps:

• Park pawl function sequence 
• Function sequence for selector lever position "P" lock 
• Function sequence of Emergency-P (see document  Emergency-P Function)  

Park pawl function sequence 

The automatic transmission is shifted to gear range "P", when the driver opens the driver door after switching off the engine. The left front door control unit (N69/1) transmits the status of the left front door via interior CAN (CAN B), electronic ignition lock control unit, chassis FlexRay, powertrain control unit and drive train CAN to the fully integrated transmission control unit. The vehicle is secured mechanically by blocking the park pawl gear in the automatic transmission.

Function sequence for selector lever position "P" lock 

A gear range change from the "P" position cannot be executed if the following conditions are fulfilled:

• No enable signal for the drive authorization system stage 4 (FBS4)
• Brake pedal not actuated
• "Circuit 15 ON" inactive

The enable signal from the drive authorization system is sent from the electronic ignition lock control unit via chassis FlexRay, powertrain control unit and drive train CAN.

	Electrical function schematic, Key-P		PE27.19-P-2058-97DAS
	Emergency-P function		GF27.10-P-3029ANO
	Overview of system components of automatic transmission (AT)		GF27.10-P-9992ANO