968 Cabriolet L4-2990cc 3.0L DOHC (1993)
^ Start interlock feature
It must only be possible to start the engine in the P and N selector lever positions. Check selector lever switch to ignition switch cable.
^ Several faults
If several faults occur, this may be due to a missing ground lead (e.g. the common ground lead of the sensors at Tiptronic control unit pin 44),
ground of body engine/transmission.
^ Gear shift function
In the event of faults in the gear shift function, check position switch (Test point 12). If the gear indicator shows the gear selected but the
transmission does not shift to this gear, there may be a mechanical or hydraulic problem.
^ Emergency operation, engine stalls. Fault memory: empty, "Rpm signal DME" and/or "Change of ignition timing" and/or "Throttle plate signal",
check Motronic voltage supply.
^ Brake light switch
If engine speed drops too much after stop-and-go driving and braking (e.g. at traffic lights), the signal from the brake light switch to the Tiptronic
control unit or the DME control unit may be missing.
Diagnosis Start Here
START OF DIAGNOSIS
To assess a Tiptronic transmission for which complaints have been received, the information about the fault and the fault occurrence should be as
complete as possible.
To avoid extra damage during test drives or faulty diagnosis results, the following items must be checked and corrected (if required) prior to the test
drive:
-. Read out fault memory with System Tester 9288 and correct fault.
-
Check that battery, connectors, and ground points are O.K.
-
External damage, leaks at transmission (ATF leaks) or final drive (hypoid oil loss), disconnected cables.
-
ATF level in transmission correct, fluid is neither dirty nor does it leave a burning smell. If ATF is dirty or if it leaves a burning smell, it is
recommended to replace the Tiptronic transmission if complete removal of the dirt residues cannot be ensured. In addition, the coolant lines and
the cooler must be flushed.
-
Engine operation, full opening of throttle when accelerator is in full-throttle position.
NOTE:
-
If a system fault occurs, the Tiptronic system shifts into a reduced driving program. The warning lamp comes on and the automatic system
shifts to 4th gear, irrespective of the selector lever position.
-
As 4th gear establishes a rigid connection between engine and final drive, you must shift to "N" at a speed of about 30 kph to prevent the
engine from stalling. When the vehicle has stopped, turn the engine off.
-
When you start the engine again, only 2nd gear and reverse are available.
CAUTION: The reverse gear interlock monitor is inoperative. Do not shift into "R" while the vehicle is in motion.
The test drive
The test drive should be used to check if the customer complaint situations actually occur when the vehicle is driven. It is actually preferable to
have the customer drive the car and to check for any potential faults, malfunctions or even for incorrect operation by the driver.
Check all functions of the transmission during the test drive:
^
All shifts, including in kickdown position in the automatic gate, as well as shifts in the manual gate
^
Various driving speeds
^
Driving in reverse (uphill if possible)
^
Stall speed
Make your diagnosis using the "Troubleshooting the Tiptronic transmission" section and determine the type of repair required.
This diagnosis plan is based on the fault memory contents. If no fault is stored although a malfunction is present, the troubleshooting plan for the
mechanical/hydraulic section should be used. Troubleshooting requires that the person performing the tests:
^ is familiar with the location of components, operation and technical relationships of the systems being tested (refer to Model Information)
^ is able to read and evaluate Porsche wiring diagrams
^ knows the functions of circuits and relays
