Faults that cannot be detected by selfdiagnosis

The Tiptronic control unit cannot detect and store all potential faults.

If a fault is found and if no fault has been stored, the tester may be used to run a system check to indicate any faults that may be present.

Some of these faults are stated below.

• No diagnosis possible, test point 0

No diagnosis is possible if the diagnostic leads are faulty

If terminal 30 is inoperative, all faults that may have been stored are erased after the ignition is switched off.

If terminal 15 is inoperative, the system enters the (mechanical-hydraulic) emergency mode. The fault lamp does not come on.

• DME rpm signal is missing. Test point 5: Actual values, connector to DME

• 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 form the brake light switch to the Tiptronic control unit or the DME control unit may be missing.

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

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