GF27.10-P-2008AHK Shift-Lock, Function
GF27.10-P-2008AHK Shift-Lock, Function
- TRANSMISSION 722.904 /906 /907 /999 in MODEL 171.4 as of Model Year 09 /Modification Year 08 model refinement package
Function requirements, Shift-Lock, general
^ Circuit 15 ON
^ Brake pedal operated
^ Vehicle speed greater than 8 km/h
Shift-lock in general
The term shift lock combines the functions which, in addition to the parking brake, offer an additional safeguard for the vehicle to prevent it moving off unintentionally.
Shift-lock function sequence
The function sequence is subdivided into the following steps:
^ Park pawl
^ Locking ignition switch
^ Locking of selector lever position "P"
^ Shift lock override (Manual unlocking, selector lever position "P")
Park pawl
The park pawl only allows shifting out of selector lever position "P" when the ignition key (transmitter key (A8/1)) switches the ignition ON and the brake pedal is pressed.
In order to ensure that after parking the vehicle, the selector lever is shifted into selector lever position "P", the transmitter key can only be removed from the electronic ignition switch control unit (N73) in this position. The vehicle is secured mechanically by blocking the park pawl gear in the transmission.
In the event of mechanical or electrical faults the selector lever position "P" can be unlocked manually (shift lock override).
Locking ignition switch
The mechanism of the ignition lock interlock connects the selector lever of the floor shift with the ETC control unit. It prevents the transmitter key from being removed when selector lever position "P" is not engaged.
The electronic ignition switch control unit mechanically locks the transmitter key at ignition ON and when the vehicle speed is greater than 8 km/h.
As soon as the vehicle speed exceeds 8 km/h, the electronic ignition switch control unit prevents any removal of the transmitter key, because automatic engagement of selector lever position "P" by the electronic selector lever module control unit (N15/5) cannot be performed.
As long as the vehicle speed remains below the speed threshold, the transmitter key can be removed. Selector lever position "P" is automatically engaged by the electronic selector lever module control unit.
Locking of selector lever position "P"
The selector lever remains locked in position "P" if the following conditions are not met:
- No power supply from electronic selector lever module control unit
- No enable signal from the drive authorization system (DAS 3)
- Brake pedal not actuated
Upon reception of a valid drive authorization code from the electronic ignition switch control unit (N73) and if the brakes are detected by the ESP, SPS [PML] and BAS control unit (N47-5) via the engine compartment CAN (CAN C), the electronic selector lever module control unit actuates the locking solenoid for the backup and park pawl (Y66/1).
The locking solenoid enables the selector lever and thus enables a shift out of selector lever position "P".
Shift lock override
View of selector lever module from left rear
90 Lever
If it is not possible to engage a gear range from selector lever position "P", because of a mechanical or electrical malfunction, then the selector lever position "P" lock has to be manually unlocked.
To do this, the stowage compartment in the center console must be unclipped and, using a suitable tool, the guide located underneath pressed onto the lever (arrow). The selector lever position "P" lock is released via a bolt in the lock solenoid valve.
When the lever and selector lever are operated simultaneously the selector lever can be shifted out of selector lever position "P".
