Non-Detectable Faults

The ECU 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.

^ Terminal 15, Test point 1
If terminal 15 is inoperative, the system enters the (mechanical-hydraulic) emergency mode. The fault lamp does not come on.

^ Terminal 30, Test point 2
If terminal 30 is inoperative, all faults that may have been stored are erased after the ignition is switched off.

^ DME rpm signal is missing. Test point 2: Actual values, connector to DME.

^ Tiptronic is in emergency mode, warning lamp comes on. No Tiptronic diagnosis possible. If all above items are o.k.: Replace ECU.

^ Transmission oil level o.k.?

^ 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 ECU pin 44), ground to body engine/transmission.

^ Gear selected
If the gear selection feature is faulty, the position switch should be checked (Test point 13).