I hope this post helps others with the W210 transmission limp home mode issue. I recently had two problems with my 2002 W210. The first problem was that the SRS light came on. The second problem was that the automatic transmission would not shift out of what I thought was 1st but was probably second. The problem with the transmission occurred on the first start of the day after a cold night. The car has 57,000 miles on it. I searched the forums and the most common source of the transmission problem seemed to be the shift module switch inside the car. The most common source of the SRS problem seemed to be the seat sensor in the passenger seat which controls whether the passenger side airbag is activated. Since I have an Easy Care warranty I decided to take it to the local dealer. The dealer diagnosed the problem as a bad ECU unit for the transmission and a bad ECU for the SRS. The transmission ECU was $1,250.00 plus $205.00 labor. The SRS control unit was $792.00 plus $346.95 labor. To its credit, Easy Care paid for both repairs. I drove the car home. The next day I didn't drive it much but the following day I began having the same transmission limp home mode shift problem, except this time it would happen every time I would go to drive the car, probably about 4 times that day. I would have to pull over, turn it off and turn it back on to get it out of the limp home mode. Today I went to start the car to take it back to the dealer and the battery almost wouldn't turn over the motor. After a couple of tries the car started. On the way to the dealer I stopped for gas. When I left the gas station the car was in limp home mode again. I pulled over to do the restart routine to get it out of limp home mode, this time the check engine light came on. I turned it off again waited 10 seconds and restarted it. The car then shifted normally but the check engine light was still on. When I got to the dealer, I told the service rep I thought the battery was going bad and that was the source of the problem. Couple of hours later the dealer confirmed the battery was bad. The service rep said they were getting all sorts of low voltage codes. The battery was replaced and the car is running fine so far. The first time I took the car in, I told the service rep I had read a post where a guy was having similar problems with the car going into limp home mode on cold mornings and it was eventually determined that the battery was going bad and the low voltage was causing the car to go into limp home mode. The service rep is telling me that the transmission ECU unit was definitely bad and it is just a coincidence that my battery also went bad. The SRS light has never come back on again since the SRS control unit was replaced. My recommendation for anybody having problems with their transmission going into limp home mode is to check your battery. I would expect that this would be a common problem and I am surprised that the dealer didn't check the battery first.

 

can charge some second party warranty company nearly 3 grand and not check limp mode because of low voltage conditions,they will. Not all dealers but a lot of them. Heck they do it to customers paying out of pocket.
everyday.