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

Transmission 725.0 in model 166 

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:

• Status of "Circuit 15 ON" from electronic ignition lock control unit (N73) (transmitter key (A8/1) inserted) over chassis CAN 1 (CAN E1), CDI control unit (N3/9) or ME-SFI [ME] control unit (N3/10) and drive train CAN (CAN C).
• Service brake status from Electronic Stability Program control unit (N30/4) over chassis CAN 1, CDI control unit or ME-SFI [ME] control unit and the drive train CAN.
• Vehicle speed signal from instrument cluster (A1) over chassis CAN 2 (CAN E2), electronic ignition lock control unit, chassis CAN 1, CDI control unit or ME-SFI [ME] control unit and the drive train CAN.

The vehicle speed is calculated using the wheel speed signals.

If the transmitter key is turned to position "0" (circuit 15 C) and removed while the vehicle is driving or rolling, the automatic 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:

• Function sequence for park pawl (except CODE 889 (KEYLESS-GO) or CODE 893 (KEYLESS-GO start function)) 
• Function sequence for park pawl (with CODE 889 (KEYLESS-GO) or CODE 893 (KEYLESS-GO start function)) 
• Function sequence for selector lever position "P" lock 
• Function sequence of Emergency-P (see document  Emergency-P Function)  

Function sequence for park pawl (except CODE 889 (KEYLESS-GO) or CODE 893 (KEYLESS-GO start function)) 

The park pawl only permits shifting out of position "P" if the transmitter key is turned to position "circuit 15 ON" and the brake pedal is depressed. The fully integrated transmission control unit receives the command to engage the park pawl from the DIRECT SELECT lever (S16/13) via the steering column tube module control unit (N80), chassis CAN 1, CDI control unit or ME-SFI [ME] control unit and the drive train CAN.

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

Function sequence for park pawl (with CODE 889 (KEYLESS-GO) or CODE 893 (KEYLESS-GO start function)) 

On vehicles with CODE 889 (KEYLESS-GO) or CODE 893 (KEYLESS-GO start function), a shift is made to gear range "P" when the driver door is opened by the driver after parking the vehicle. The left front door control unit (N69/1) sends the status of the left front door safety catch microswitch (A85s1) over interior CAN (CAN B), electronic ignition lock control unit, chassis CAN 1, CDI control unit or ME-SFI [ME] control unit and the drive train CAN to the fully integrated transmission control unit.

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
• Transmitter key not in position "Circuit 15 ON"

The enable signal from the drive authorization system is sent from the electronic ignition lock control unit via chassis CAN 1, the CDI control unit or ME-SFI [ME] control unit and the drive train CAN.

	Electrical function schematic, Key-P		PE27.19-P-2058-97NAC
	Emergency-P function		GF27.10-P-3029ANF
	Overview of system components for automatic transmission (AT)	Transmission 725.0 in model 166 (except 166.006)	GF27.10-P-9992ANF
	Overview of system components for automatic transmission (AT)	Transmission 725.0 in model 166.006	GF27.10-P-9992ANK