I have a 97 E39 (528i) with 150K on it. When we get a significant amount of rain, the automatic transmission will begin shifting between gears as if there is a short somewhere. it'll go from D to S1, S2, S3 with out regard to rpm's or MPH. Once I let it sit and dry out a bit it's runs fine again - sometimes it happens after gooing through the auto car wash as well - so it definately seems to be pointing at a short somewhere......I just don't know what to check? The wheel sensors are all relatively new and the seal on the conector is good.....any ideas (crank shaft sensor maybe????)

I might check to make sure the cover is completely sealed in the engine compartment where the ecu and the trans computer are located. its on the passenger side underneath the air filter, maybe water is getting in there and causing problems.

I pulled the cover off of the air filter above and the drain holes in the compartment above the TCM were clogged.......so, unclogged them and waiting for rain..........hopefully that is it....THANKS!