I'm a total idiot when it comes to transmissions, except where and how to check the fluid level. Something weird happening with my '98 S90 - the "Winter/Wet" arrow warning light is flashing and the "W" and "E" shift mode buttons are flashing back and forth. Seems like the trans is not downshifting when this light show is happening. This is happening about every third day of driving like clockwork. It will start early in the morning and by afternoon, it seems to have corrected itself. Any ideas?

 

How many miles do you have on Her?
Has she gotten wet Lately? if so, blow dry all elect connections.
Do you have a MIL or Malfunction Indicating Light ?
If so, plug in your OBD scanner and see what the code is; base on this results follow the possible causes; please post results.
You can also start with resetting the transmitting computer by unplugging the +pos red side of the Battery for 2 Min. (this will also reset the main computer).
" IMPORTANT " Make sure you know the Code for the car radio before unplugging the battery. (otherwise, no more radio).
Also, try up shifting and down it manually; if OK, this eliminates a mechanical problem.
Please repost your OBD results.

 

I believe that is a common PNP switch failure. You may want to search the forum. I've seen several write ups about that problem.

 

Sorry.... what's a PNP switch?