'02 325i ZF automatic in limp mode...INPA shows erratic turbine rev sensor readings

[egiles14]

I know this isn't ZHP specific, but thought I might get some input here also.

I picked up this '02 325i this weekend that was for sale due to the transmission being in limp mode. Reverse works fine, but when you select drive and start moving forward it almost immediately goes into limp mode. The recurring code is 33 Turbine Rev Sensor. I connected my laptop running BMW INPA to it last night, and I am getting erratic readings from the turbine sensor while the car is in Park or Neutral. It should be a steady figure that is only slightly less than engine RPM, but as you can see from the below video it is erratic.

https://youtu.be/amyYULb-dsw

My first guess is that the input speed sensor inside the transmission is failing, or the wires to it are shorting/frayed. I guess it could be a slipping torque converter, but then I would imagine it wouldn't work in reverse either. I can at times use manual mode and it will drive fine for a short bit, but then will go into limp mode again.

I plan to pull the pan and check the fluid condition, as well as see what other material I might find in the pan. Does anyone have any thoughts, comments, or suggestions to help pinpoint that this might all be related to a bad input sensor?

[egiles14]

UPDATE: So as to help others, I was able to fix the problem. I pulled the transmission pan, filter, and removed the valve body. The original turbine rev sensor showed a small amount of exposed wire due to rubbing the side of the valve body. This has been mentioned here before in another post related to this problem. I replaced the sensor with a known good one, buttoned everything back up with a new filter, gasket and 8 quarts of Valvoline MaxLife synthetic ATF (which is highly regarded by ZF transmission rebuilders, and has the BMW approval on the container) and everything seems to be fixed. Using INPA to get the readings from the sensor showed a steady signal at all times. The transmission shifts perfectly smooth with no issues.

There wasn't any metal chunks or large material in the pan-only the normal tiny shavings on the magnets consistent with 151k miles. The fluid and filter were original, and the fluid was black and thin. The transmission should be good to go for many more miles now. As a matter of fact, the person I bought the car from now wants to purchase it back now that it is repaired, so he will get his car back with a MUCH lower repair bill than he would have received anywhere else.

[fredo]

That's good news. Everybody wins !

[BMWCurves]

Thanks for following up! Definitely could be useful to others.