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Home >> Mercedes Benz >> 2015 >> CLS550 Base >> Repair and Diagnosis >> Transmission >> Automatic Trans >> Automatic Transmission - 218 Chassis - 1 Of 2 >> Basic Knowledge >> Intelligent servo module for DIRECT SELECT, component description - GF27.19-P-4020AHQ

Intelligent servo module for DIRECT SELECT, component description - GF27.19-P-4020AHQ

MODEL 218 with TRANSMISSION 722.9 (except 722.931) 

Automatic transmission viewed from left 

Fig 1: Identifying Intelligent Servo Module For Direct Select
G10083006Courtesy of MERCEDES-BENZ USA

Location 

The intelligent servo module for DIRECT SELECT is mounted on the left of the transmission housing in the direction of travel.

Task 

The task of the intelligent servo module for DIRECT SELECT is subdivided into the following subtasks:

General 

The driver's gear range request "P", "R", "N", "D" is not transmitted from the control to the transmission via a rod (mechanical connection) but by means of an electronic connection ("wire"). This electronic connection consists of the DIRECT SELECT lever (S16/13) and the intelligent servo module for DIRECT SELECT. The overall system is called "Shift-by-wire". The intelligent servo module for DIRECT SELECT controls the main motor and the emergency motor.

IMPORTANT The intelligent servo module for DIRECT SELECT measures the position of the eccentric shaft via the eccentric shaft position sensor and the actual position of the range selector lever via the angle sensor.

Input and output signals 

The intelligent servo module for DIRECT SELECT evaluates the following input signals and outputs the appropriate output signals:

Direct input signals 

Direct output signals 

CAN input signals 

Electronic Stability Program control unit (N30/4) (except code (233) DISTRONIC PLUS and model 218.374/974) or Premium Electronic Stability Program control unit (N30/7) (with code (233) DISTRONIC PLUS or model 218.374/974) 

Electronic ignition lock control unit (N73) 

Front SAM control unit with fuse and relay module (N10/1) 

Fully integrated transmission control unit (Y3/8n4) 

CAN output signals 

Control unit for fully integrated transmission control (Y3/8n4) 

Instrument cluster (A1) 

Shown in range selector lever position "N" 

Fig 2: Identifying Selector Lever Position "N"
G10083007Courtesy of MERCEDES-BENZ USA

Function 

The main motor is actuated and the worm shaft is turned via the drive belt and the two drive pulleys. The carriage moves to the required position and the range selector lever assumes the specified position selected.

The actual position is detected by the angle sensor and sent via the drive train CAN to the fully integrated transmission control unit.

IMPORTANT At "circuit 15 ON" the intelligent servo module for DIRECT SELECT routes the selector lever position sent by the fully integrated transmission control unit over the drive train CAN and chassis CAN to indicate the gear (A1p12) in the instrument cluster. At "Circuit 15 OFF", the intelligent servo module for DIRECT SELECT sends the selector lever position sent by the steering column tube module control unit (N80), to the gear indicator.

With "circuit 15 OFF" and vehicle standstill, selector lever position "P or N" is engaged, as soon as the transmitter key (A8/1) is removed from the electronic ignition lock control unit.

On vehicles with code (889) Keyless Go, the request for selector lever position "P", with "circuit 15 OFF" and the vehicle at a standstill is made as soon as the driver door is opened.

If selector lever position "N" is engaged before "Circuit 15 OFF" and the driver door is opened after "Circuit 15 OFF", selector lever position "N" remains engaged.

Technical data
Designation
Unit Value Tolerance range Remarks
Intelligent servo module for DIRECT SELECT (A80)         
Power supply V 13.5    
Voltage limit: minimum V 9.0    
maximum V 16.0    
Power consumption: Stand-by mA 200    
Operation A < 30    
Extended operation A 40   Maximum 300 ms
Quiescent current mA 0.2    
Reverse polarity protection       No
Operating temperature range °C -40 - 140    
Adjustment times between gear ranges ms 300   "P and D"
ms < 150   "N and R"
ms < 150   "N and P"
ms < 150   "N and D"
Flash capability/coding capability       Yes/yes
REFER TO SYSTEM WIRING DIAGRAMS Wiring diagram for intelligent servo module (ISM) control unit A80 PE27.60-P-2101-97XAA