Hello everyone,

I recently purchased a nice 1998 S90. The car had the famous blinking arrow and mode selector light flashing. The CEL was also on.

When first started the car drove fine but quickly lost forward or reverse movement. The engine would rev but the car would barely move. After the engine was shut off for a minute or two it would again shift and move for a mile or so before repeating the same transmission failure.

I have done considerable research on this condition that led me to the PNP switch.

I am a fair shade-tree mechanic and I had no difficulty dropping the exhaust and removing the switch. After considering the investment required to purchase a new switch, I opened the old one up and cleaned it thoroughly and relubed it with the proper grease. After I installed the switch, the flashing arrow disappeared and the mode switch was again functional. The shifter locked into all the gears and the backup lights and beeper worked as designed. The car started while in park with no problems other than the worn ignition switch that needs to be fiddled with to get the shift lock to disengage.

However, the drivability problem remained along with the CEL.

I have a bluetooth OBD2 diagnostic tool that I normally use along with the Torque Pro android app. This allowed me to see the real-time operating status of the car but would not display any fault codes. Nor would it erase whatever code was causing the CEL to be lit.

I found an app on line(Carista) that will display and reset the fault codes on older Volvos. The fault codes were P0740 and P0733 and after being reset they did not appear again, although I did not drive the car normally but just tested it in the driveway.

Still, the same transmission malfunction exists. It will start and move and shift normally for a short distance then lose all transmission function. This is repeated again after a minute with the key off.

The transmission fluid is bright red and does not smell burned. The fluid level is fine. There are no odd noises or clunks from the drivetrain. I seems to me that this is an electrical control problem and not an internal transmission fault.

I have ordered a replacement PNP switch that will be here next week. In the meantime I would appreciate any input that y'all have on this problem. Do you think that the PNP switch is still to blame? Do I need to drop the pan and possibly replace the filter? Could this be a failure to maintain fluid pressure?

I have no funds to have it professionally repaired as I am retired and on a fixed budget, but I can and will do the work myself if I can just figure out where the problem lies.

Thank you all for reading this WOT!

Please give me your opinions!