Wendymomof2

Hello all! I've got a problem with my 1999 ML320. After returning from a 1400 mile trip I left my sunroof open and it rained a lot in my car.... Every since then it won't go over 30mph! I have been reading the forums and discovered this is called "limp home mode". My boyfriend has run the scan tool on it and the only fault codes that appear has to do with the O2 sensor. None related to the transmission. It won't shift into 3rd gear. It gets up to 30 mph and from there if I try to go faster the engine revs higher rpms but doesn't go into gear. What could this be? So far. We have changes the fluid. After some extensive research it seems like it could be the gear shift module? Or perhaps the auxiliary battery? What and where is the auxiliary battery? Any advise or data would be greatly appreciated. Thank you!

DUTCH

Sorry. Wrong forum. 1999 is a W163, I think.