This is a very odd, very specific problem. My 2002 E46 M3 is shifting into "0" while shifting, and ignoring all input at random(gas, paddles/shifter) for about 10 seconds before returning to the last gear it was previously in. For reasons that are too long to go into, I know for a fact the problem is not the hood pins or the programming. The car won't do it until after it's been driven for about 15 minutes in weather over or around 80 degrees F. It's definitely a temperature-related issue, as the car will not act up in cold weather. A while ago, the car took a nasty trip through a few inches of water on a backroad. Since then, it's had this problem. My theory is one of the two temperature sensors for the hydrolic fluid entering the transmission oil cooler got wet(apparently they sit low on the cooler, just infront of the radiator, close to the ground) and later coroded, giving the SMG computer false values and thus giving it the illusion that the SMG system is "overheating" when, in fact, it's not. Temperature is a definite in the problem. Has anyone ever heard of this rare, weird problem before? If so, does anyone agree with me about the temp sensors? Thank you all!
I had a similar problem with my 2003 E46 M3 Cab SMG. When the car was hot, and I was driving it aggressively, the transmission would drop to "0" (neutral) when I selected a gear. It didn't happen on every drive, but I could recreate the issue with some aggressive driving on any given hot day (I live just north of Atlanta, so there are plenty!). I discovered this issue soon after buying the car in October 2007, but the issue disappeared over the winter. I hoped it was gone for good, but after a few warm spring days earlier this year, it began happening again. I took the car to two different dealers who spent a lot of time changing out inexpensive relays and then giving me the car back with the issue still happening (I think they were not up for driving a customer's car aggressively to see if the issue was truly resolved). Finally I took the car to an independent BMW shop that is also one of only two Dinan shops in the Atlanta area and they diagnosed replacement of the SMG Hydraulic Unit (pump). I actually had the pump replaced at a dealer -- incase that wasn't the problem, dealers are more likely to back their diagnoses/work even if more work needs to be done. But that was it... I haven't had the problem since and the car has been rock solid for 5 months of so. The bad news is it cost about $3000 (and that's with the BMW CCA 10% discount on the part). So have them replace some of the inexpensive relays (or perhaps temperature related sensors, etc.) first, you may get lucky, but you may end up where I did in the end.
