Emergency-P Function - GF27.10-P-3029ANE
Transmission 725.0 in model 463
Sectional view of electrohydraulic park pawl actuation
Function requirements, general
- Vehicle stationary
- Terminal 15 ON
The electronic ignition lock control unit (N73) transmits the status of circuit 15 via the chassis FlexRay (Flex E), the powertrain control unit (N127) and the drivetrain CAN (CAN C1) to the fully integrated transmission control unit (Y3/8n4).
Emergency-P
The park pawl is automatically engaged if communication faults occur with the fully integrated transmission control unit (e.g. undervoltage in on-board electrical system or open circuit).
If a malfunction occurs, the electronic ignition lock control unit actuates the park pawl lift solenoids in the controller unit for the fully integrated transmission control (Y3/8). The voltage for this is provided by the park pawl capacitor (C8) via the Emergency-P path. The electronic ignition lock control unit switches the voltage through to the fully integrated transmission control unit. The park pawl lift solenoid lifts the detent lever (11 d) of the parking lock actuator out of locking contour "P" (11 c) or out of locking contour "not P" (11 e). The piston rod (11f) is then no longer engaged. The transmission oil can leak out of the pressure chamber ("Not P"). If required, the lubrication pressure solenoid (Y3/8y12) is energized through the park pawl lift solenoid. The compression spring (11l) then moves the piston rod (11f) in the direction of the park detent. When doing so, the compression spring (11l) supports itself on the piston housing (11). As a result of the increasing profile of the park pawl cone (11), the 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 (11k) and is in the ready position. If the parking lock gear continues to turn, the park pawl is engaged.
The park pawl lift solenoid is actuated in pulses to minimize noise in the vehicle. With Emergency-P, actuation takes place via the electronic ignition lock control unit.
If the park pawl lift solenoid malfunctions, the notch lever release pin (11g) can be moved hydraulically. When the engine is at a standstill, the required oil pressure is generated by the transmission oil pump (M42).
| Overview of system components for automatic transmission (AT) | GF27.10-P-9992ANE |