Intelligent servo module (ISM) component description - GF27.19-P-4015SXA

TRANSMISSION 722.6 in MODEL 216, 221 up to Model Year 08 

Location 

The intelligent servo module for DIRECT SELECT is mounted on the left in the direction of travel on the transmission housing. The intelligent servo module for DIRECT SELECT has an integrated range selector lever and replaces the range selector lever used previously.

Task 

The intelligent servo module for DIRECT SELECT reads in the following internal sensors:

• Angle sensor which records the actual position of the integrated range selector lever
• Angle sensor, which records actual position of eccentric shaft

In addition there exists via the Controller Area Network (data bus/CAN bus) (CAN) a connection to the:

• Instrument cluster (A1), via the central-CAN
• ESP control unit (N47-5), via the chassis CAN
• Central gateway control unit (N93), via the chassis CAN
• ETC [EGS] control unit (N15/3), via drive train CAN
• EIS [EZS] control unit (N73), via chassis CAN
• Steering column module (N80), via the chassis CAN

The intelligent servo module for DIRECT SELECT actuates the following components depending on processed input signals:

• Main motor
• Emergency motor

The ME-SFI [ME] control unit (N3/10) is the interface between the drive train CAN and the chassis CAN, the central gateway control unit is, amongst other things, the interface between the chassis CAN and central CAN.

This involves the processing of the following data from other systems: 

ESP control unit 

• Speed information, for R/D-lock function
• BAS release switch (A7/7s1), for P-lock function

EIS [EZS] control unit, on model 221 up to 31.8.06 

• Request of gear selector switch position "P", at "Circuit 15 OFF" and vehicle standstill position "P" is engaged, as soon as the transmitter key (A8/1) is removed from the EIS [EZS] control unit
• On vehicles with code (889) Keyless Go the request of gear selector switch position "P" also ensues with "circuit 15 OFF", vehicle stationary and driver door open

EIS [EZS] control unit, on model 221 as of 1.9.06 and on model 216 

• Request of gear selector switch position "N", with "terminal 15 OFF" and vehicle stationary position "N" is engaged as soon as the transmitter key is removed from the EIS [EZS] control unit
• Request of gear selector switch position "P" with "terminal 15 OFF", vehicle stationary and driver door open

If gear selector switch position "N" is engaged before "terminal 15 OFF" and the driver door is opened after "terminal 15 OFF", gear selector switch position "N" remains engaged.

Central gateway control unit 

• Feedback "Circuit 54 ON", as supplemental information for P-lock function

EGS control unit 

• Specified position of range selector lever

The following information is passed to other systems: Instrument cluster 

• Gear selector switch position, with "circuit 15 OFF" the intelligent servo module for DIRECT SELECT passes on the gear selector switch position transmitted by the steering column module to the gear indicator (A1p12)
• Gear selector switch position, with "circuit 15 ON" the intelligent servo module for DIRECT SELECT passes on the gear selector switch position transmitted by the steering column module to the gear indicator

EGS control unit 

• At "Circuit 15 ON" actual position of range selector lever

Design, shown in range selector lever position "N" 

Function 

The main motor is actuated and the drive pinion gears induce the threaded spindle to rotate. The slider moves into the requested position and the range selector lever assumes the given specified position.

The actual position is recorded by the angle sensor and is passes on to the ETC [EGS] control unit via the chassis CAN.

Emergency-P function, start position 

The starter battery (G1/4) supplies the emergency motor with voltage by way of the EIS [EZS] control unit in an emergency, e.g. in event of undervoltage in on-board electrical system. This in turn causes the eccentric shaft to turn.

Emergency-P function, intermediate position 

The rotating eccentric shaft presses down onto the release studs of the left carriage half. This in turn causes the mechanical connection between the left and right carriage halves to be broken.

Emergency-P function, end position 

The pre-compressed coil spring pushes the two carriage halves apart. The right slider half slides along the threaded spindle to the right and presses the range selector lever into position "P". The eccentric shaft continues to rotate, until the emergency motor is no longer actuated. The actual position of the eccentric shaft is recorded by the positions sensor for the eccentric shaft and sent to the electronic circuit.

The emergency P-function is automatically overridden, if the emergency case, which, e.g. is caused by undervoltage in the on-board electrical system, is no longer given. The main motor drives the threaded spindle by way of the drive pinion gears. The left carriage half runs on to the right carriage half, the coil spring is pre-compressed again and the mechanical connection made again.