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

Transmission 725.0 in model 463 

Function requirements, general 

• Circuit 15 ON
• Service brakes operated
• Vehicle speed below 8 km/h

Key-P function in general 

The designation Key-P comprises all the functions that along with the parking brake serve 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:

• Circuit 15 ON status

  The electronic ignition lock control unit (N73) sends the status of circuit 15 over the suspension FlexRay (Flex E), powertrain control unit (N127) and the drive CAN (CAN C1) to the fully integrated transmission control unit.

• Service brake, status

  The Electronic Stability Program control unit (N30/4) sends the status of the service brake via the chassis FlexRay, powertrain control unit and drivetrain CAN to the fully integrated transmission control unit.

• Vehicle speed

  The instrument cluster (A1) sends the vehicle speed via the user interface CAN (CAN HMI), the electronic ignition lock control unit, the chassis FlexRay, the powertrain control unit and the drivetrain CAN to the fully integrated transmission control unit.

The Key-P function is subdivided into the following points:

• Park pawl 
• Locking of selector lever position "P" 

Park pawl 

The park pawl only permits shifting out of position "P" through the DIRECT SELECT selector lever (S16/13) at "circuit 15 On" and when the brake pedal is operated. The steering column tube module control unit (N80) reads in the DIRECT SELECT lever switch position directly and sends it over the chassis FlexRay, powertrain control unit and the drivetrain CAN to the fully integrated transmission control unit. The fully integrated transmission control unit then controls engagement of the selected gear range.

Drive range "P" is automatically engaged when the driver opens the driver's door after switching off the engine. The left front door control unit (N69/1) sends the status of the left front door over the interior CAN (CAN B), electronic ignition lock control unit, suspension FlexRay, powertrain control unit and the drive CAN to the fully integrated transmission control unit.

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

Locking of selector lever position "P" 

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 OFF

The electronic ignition lock control unit sends the drive authorization system enable over the suspension FlexRay, powertrain control unit and the drive CAN to the fully integrated transmission control unit and to the CDI control unit (N3/9) or the ME-SFI [ME] control unit (N3/10).

	Electrical function schematic, Key-P		PE27.19-P-2058-97ZGB
	Overview of system components for automatic transmission (AT)		GF27.10-P-9992ANE