copied from BF; Car 1999 E36 M3. My car hates cold weather - AC/CEL only when it's cold
I'm the relatively happy owner of a 99 M3 convertible with 110,000 miles. It's an auto, and it has run like a dream from April (when I bought it) until just recently when it started getting cold. First the transmission started shifting funny, then the ASC light would come on occasionally (usually in conjunction with the tranny shifting funny), then last week when it got really cold the CEL light came on. Codes included P1765 and P0121. I have checked for vacuum leaks and replaced the TPS as well as tested it. All good. Then yesterday the temps got back up above 50 degrees. No CEL, no ASC, and it ran great.My car has spent most of its life in SoCal, Alabama, and now briefly in the Louisville KY area. I'm convinced it doesn't like cold weather, but I'm trying to figure out what is really going on. Any ideas?
has the auto trans fluid been changed lately? Filter? Cold weather should not affect the operation other than the trans holding gears slightly longer.
What TPS did you get to replace yours? They are usually the cause of erratic shifts, but with the P1765 it could be a relay or loose connection. Since it is temperature related, remove your relays 1 at a time and make sure the contacts are clean and making a good connection. Wait until the outside temp drops to where you can duplicate the problem and see if it still happens.The other quick and easy check is the trans electrical plug where it goes into the trans. Disconnect it, look for green meanies(corrosion) or fluid leaking out of the pins. Clean with electric contact cleaner and reconnect. Do one or the other not both and report back.
Thank you guys. The transmission fluid and filter was changed last year before I bought the car. I bought the TPS off of Amazon, and I think it was the generic OEM brand. I have tested the resistance and the voltage output during throttle operation, and it seems fine and within specs, but I did this after the problems started. So either the old one was bad and so is the new one, or it's something else.
Today I had a CEL on the way to work, and none on the way home - because it warmed up outside. I also checked the battery tonight, and everything seems fine and it is charging nicely even with everything in the car turned on. With every powered option turned on and running at full blast, the battery was still hitting 13.1 at idle, and 13.9 at 2000 rpms. I'll start checking relays and plugs when the symptoms start showing up again.
So a quick update to close the loop on this thread. I decided to go back and re-test the throttle position sensor. Even though it kept testing out correctly for resistance and voltage, all of the signs during drivability kept pointing back to a problem with the TPS. So I broke down and bought the most expensive TPS I could which of course is the OEM BMW part. After running it now for a week the car has never performed better. All of the lights on the dash are gone. And it feels as happy as itís ever been. Lesson learned, by the right parts in the first place.