Emergency-P Function - GF27.10-D-3029TSA

Transmission 725.0 in model 907

Sectional view of electrohydraulic park pawl actuation

Function requirements, general

Vehicle stationary
Circuit 15 ON

The electronic ignition lock (EZS) control unit (N73/8) sends the circuit status of circuit 15 to the fully integrated transmission control (VGS) electric controller unit (N15/15).

Emergency-P

The park pawl is automatically engaged if there are disruptions in communication with the fully integrated transmission control (VGS) electric controller unit (for example, undervoltage in the on-board electrical system or open circuits).

If a fault occurs, the electronic ignition lock (EZS) control unit actuates the park pawl lift solenoids (N15/15l1) in the fully integrated transmission control (VGS) electric controller unit. The voltage for this is provided by the park pawl capacitor via the Emergency P path. The electronic ignition lock (EZS) control unit switches the voltage through to the fully integrated transmission control (VGS) electric controller unit.

The park pawl lift solenoid lifts the detent lever (11 d) of the parking lock actuator out of locking contour "P" (11c) or out of locking contour "not P" (11 e). The piston rod (11 f) is then no longer engaged. The transmission oil can leak out of the pressure chamber ("Not P"). If required, the lubrication pressure solenoid (N15/15y12) is energized through the park pawl lift solenoids.

The compression spring (111) then moves the piston rod (11f) in the direction of the park detent. When doing so, the compression spring (111) supports itself on the piston housing (11). As a result of the increasing profile of the park pawl cone (1the park detent is raised and pressed against the park pawl gear.

If the tooth of the park detent does not end up in a tooth space when the vehicle is stationary, but on a tooth of the park pawl gear, the park pawl cone (11j) is pre-compressed by the spring of the rod (11 k) and is in the ready position. If the parking lock gear continues to turn, the park detent engages in the next tooth space.

The park pawl lift solenoid is actuated in pulses to minimize noise in the vehicle. For Emergency-P, actuation takes place via the electronic ignition lock (EZS) control unit.

If the park pawl lift solenoid malfunctions, the notch lever release pin (11 g) can be moved hydraulically. When the engine is switched off, the electric auxiliary oil pump (M42) generates the required oil pressure.

Overview of system components of automatic transmission (AT)

GF27.10-D-9992TSA