Hi! My name is Melanie and I have a 2004 325ci. The car will hesitate when first started and not move. It’s as if the car is in neutral when I step on the gas as the engine revs and then all of the sudden it jumps into gear and takes off. I had it checked last year for the first time and I was told it was the transmission, that didn’t set well with me as that is $5k. I took it to the dealership and they re-programmed it and that helped some as it was August and made it much less noticable and then it went away as we were moving into the cooler months. I live in Vegas and it is starting to approach those 3 digit temps and the problem is back. It only happens in the warmer temperatures. When I first bought the car in '06 it would have this problem every now and again and it wasn’t consistant. Now its very noticable and driving me crazy! There has to be another reason besides a re-program??? i know the people in the parking garage are wondering why this lady can’t drive a stick shift!
From your description, it sounds like the speed sensor has failed in the transmission. That is a moderately expensive repair because the valve body in the transmission has to be removed to get to it, but no where near $5k. I would expect somewhere between $1k and $2k, depending on the mileage and how much more they want to do do be confident in guaranteeing their work.
Other common problems with this transmission are the temperature sensor (less labor to get to) and anything that causes the electrical supply to the transmission computer to be erratic.
More serious transmission problems can also give your symptoms, but if you had those problems, the symptoms would not come and go, and reprogramming the computer would not have helped.
More info - quoted from e46Fanatics by way of UnitedBimmer.com:
Transmission Input and Output Speed Sensors:
The transmission speed sensors (turbine and output shaft) are analog inductive
sensors that produce an AC sine wave similar to an ABS/ASC wheel
speed sensor. The AC signal frequency is proportional to the rotation speed
of the monitored components .
• The turbine speed sensor scans a pulse wheel attached to the forward clutch housing.
• The output shaft speed sensor scans a pulse wheel attached to the rear ring gear.
The GS 20 monitors these signals along with the engine speed signal (CAN) to calculate
transmission slip ratio for plausibility and for the adaptive pressure control function.
The sensors are monitored for plausible signals, opens and shorts. Specific fault codes are
stored for defects with these sensors.
These links are part diagrams showing you where it is located.