Car is 2004 XC90, D5, 163hp with the AW55-50 transmission.
The problem I'm trying to solve: When I'm doing more than 80 kmh (50 mph) sometimes the dashboard will display a single dash instead of the gear position. To fix this, I'd fully stop, turn off the ignition and start again. I've noticed it only happens when going uphill. So if I'm going downhill or the road is flat, it never happens. Also I get the following code (using vida): TCM-002F Lock-up function slipping or not engaged

Now, my hypothesis is that the torque converter lock-up clutch is worn out (explains why it only happens when going above certain speed). Maybe not worn out enough to prevent normal operation. But when going uphill, that is an extra load, so it starts slipping and the transmission is put into emergency mode (I assume).

Since I'm looking for the easiest possible solution to this, how do I stop the lock-up clutch from engaging (and causing trouble)?
My only idea so far is to try and mess with the transmission oil temperature sensor. I believe that the clutch never locks if the oil is still cold. But still, only a theory.

Thanks.

 

Hi, How did you get on with this. Im having the same problem here and dont want to pay for a new transmission.

 

If the car is new to you, I'd do a drain/fill making sure to use the correct transmission fluid as spec'd in the owners manual - just in case somebody used the wrong type of transmission fluid. Have you checked the transmission fluid level/color yet? As to the OP'rs comment about being able to stop/start the car to do a reset suggests it may be a TCU connection or the lock-up solenoid versus a mechanical issue within the transmission.