Transmission Mode Switch: Description and Operation

Shift Lever Module (726)

Location
In gear selector unit.

Main Use
To inform TCM that gear position M has been selected.

To inform TCM through a direct line that manual gear changing up or down is requested.

To inform Ignition switch module that gear position P has been selected.

To indicate with LEDs in the gear selector coulisse the gear position that is currently selected, P-R-N-D or M.

Type
Microprocessor with integrated Hall sensor.

Activation
The SLM control module is powered with +30 on pin 2 from the electrical centre 22, fuse 5. Grounding is done on pin 3, grounding point G41. Bus communication (I-bus) takes place on pin 12.

Communication regarding gear changes up or down in position "M" takes place from pin 7 on the SLM to pin 3 on TCM for FA 57 respectively pin 8 on TCM for AF 40.

Communication is resistive multiplexed. SLM has an internal 8.2 kohm resistor to B+ connected to the pin. This is connected in parallel with another resistor of 1.5 kohm when changing down. When changing up, a resistor of 4.4 kohm is connected. There is a 390 ohm resistor to ground in TCM. In this way, 3 normal voltage levels are generated corresponding to a untouched gear lever, M- and M+. Other voltage levels give a diagnostic trouble code.






Power supply, ground and bus connection






Communication with TCM