Control Module: Description and Operation

ELECTRONIC CONTROL UNIT:

The principal input and output signals:

The 88-pole transmission control unit is installed at the rear of the luggage compartment at the engine partition panel (next to the DME control unit). Diagnosis can be performed on this control unit using the Porsche System Tester 2.

The Multifunction Switch:



The multifunction switch is attached to the transmission and does not have to be adjusted.
9 of the 10 pins on the switch are assigned. The lines 1 - 4 are reserved for the information sent to the Tiptronic control module regarding the position of the selector lever. If the selector lever is at an intermediate position (e.g. Z 1 = R flashes), the indicator flashes.
A coding system is required so that all of the information can be carried by these 4 lines.

Coding of Positions:




Data line from Tiptronic control module
The information for the display in the instrument cluster for actual gear, M or B program, and replacement program is sent from the Tiptronic control unit (pin 25) through the wiring harness.

Specification:
Signal type Pulse-width modulated (PWM)
Frequency 50 Hz
Level 0 - 12 V

Signal Coding:




Special conditions
- No display for actual gear, but no fault stored 70%
- Fault stored in Tiptronic control unit Beyond the above range

Note:
The instrument cluster cannot distinguish between a faulty line (between Tiptronic control unit and instrument cluster) and the limited driving program.

Data exchange between DME and Tiptronic control unit
The signals between the DME and Tiptronic are exchanged via CAN-BUS* lines, i.e. data blocks are transferred via two lines.
These data blocks contain, for example, the following information:
DME - Tiptronic: Engine speed, engine torque, throttle position, engine temperature, OBD status, ambient conditions.
Tiptronic - DME: Torque reduction, "check engine" request (USA only), selector lever position, gear.
The data is updated every 10 ms. Transmission of the data is bidirectional, i.e. the data can be exchanged in both directions along a single line.

*CAN-BUS Controller Area Network

Data exchange between ABS and Tiptronic control unit
To be able to calculate the lateral acceleration, the Tiptronic control unit receives the speed of the front wheels (left and right) from the ABS control unit.
In addition, the Tiptronic control unit enters a special program if the information "TC (Traction Control) active" is received.