Audi Repair: Audi Tiptronic gearbox errors, tiptronic gearbox, audi tiptronic

Question
I have a 1999 Audi TDI Quattro with a Tiptronic gearbox. Occasionally the gearbox clunks into 'limp-home' mode and all the gear position indicators on the dashboard computer read-out are illuminated. The gearbox seems to lock into third gear and the torque converter lock-out doesn't operate. This happens once every few months and only when the engine is fully warmed up after ten minutes' driving and at slow speeds (stop/start traffic, for example).

Twice recently I've noticed that the torque converter lock-out hasn't operated at cruising speeds. Yesterday on a 100 mile journey when gently accelerating from 40mph back up to cruise speed (60mph) I noticed the engine revs were 400rpm higher than at the same speed previously and the fuel consumption was higher. Accelerating to 70mph and then backing off the gas to drop back down to the cruise setting seemed to solve the problem, which didn't repeat itself for the rest of the journey.

Do you think the symptoms above could be connected? Do they suggest a specific fault with a sensor or cable, or a general problem? Would appreciate any advice you can offer, Jan.
Thanks,
Ben

Answer
If all the gear positions are illuminated, this is the TCM (trans control module) signal of a code in the trans.  Get the codes read out and let's see what the computer says.  Could ba a solenoid valve internal to the transmission or a fluid issue, or perhaps just a poor connection.  Let me know what you find,  Jan