Here's a video on replacing the trans thermostat. "Warning" lot of expletives when viewing this video. LMAO

https://www.youtube.com/watch?v=7tIsX5Aciq4

Here's an article on replacing the thermostat on an X5 2000-2006. I think it is for all models.

Pelican Technical Article - BMW X5 - Transmission Cooler and Thermostat Replacing

No expletives on this article. LMAO

Thanks for the replies, guys.
Looking at the video on replacing the reservoir (yes, with lots of colorful language not found in regular shop manuals) the small two-wire sensor that goes in the bottom of the tank-that is actually a trans fluid temp sensor? That will give me another direction to go in looking at. Didn't realize that is what that was for.

Looking at Bentley manual, and in looking at the schematic for the trans valve body, it seems to show a trans temp sensor as part of the transmission position sensor (adjacent to the valve body inside the transmission) on this application. Am I interpreting that correctly?

As far as any overheating situations, I don't think that's what I have. Any time I scanned the data stream including after longer runs, I get a "-40" degree reading, which I'm assuming is because there is either a malfunctioning sensor of some sort of continuity issue.

I will try and swap out the little sensor on the bottom of the radiator over flow tank. This is good info, as I recall when I was putting the powertrain back in that the connector on the sensor had degraded a bit.
I won't get to this until the weekend. I'll post what I find out.
Thanks again, guys. Very helpful.

What actual resistance reading do you get when measuring between pins 6 & 10 on the 16-pin connector at the back of the transmission? You need to check that you get the same/similar reading when measuring at the equivalent pins at the ECU. Sorry I’m not sure about the E53 but on the Range Rover it’s pins 18 & 19 on the C1835 (40-pin) connector (black/red wire and white/red wire respectively).

http://i260.photobucket.com/albums/i...ps2d1c6330.jpg

As you say, the DTC is saying there’s an open circuit (broken wire?) giving infinite resistance and therefore a -40°C temperature reading for the fluid.

Phil

Ahahha. I found it pretty funny to watch.

Thanks for the good info, RRPhil. I will get to this on Saturday. Can you confirm that the trans fluid temp sensor is part of the trans range (position) sensor inside the trans case?

My understanding was that it was part of the loom itself, covered by the sleeving

http://i260.photobucket.com/albums/i...ibitorloom.jpg

http://i260.photobucket.com/albums/i...psmwgpjowz.jpg

http://i260.photobucket.com/albums/i...psqvvqmy8k.jpg

I’ve got one lying around somewhere – I’ll try to have a look

Phil

Ok, guys, I have been trying to get into it this afternoon. The picture RRPhil posted of the harness and transmission range selector is spot-on. That is what is inside my transmission, including the colors of each wire. I have in-hand my original harness that was removed from my transmission (taken out when I put in my new harness), plus I have removed the position range sensor from my failed transmission. My in-hand parts match the picture RRPhil has posted. I have been using a digital multi-meter on a variety of resistance settings trying to obtain readings across the pins that RRPhil mentioned in his post. I don't get any readings that make sense. I still am unsure where the oil temp sensor is in this thing. Although RRPhil mentions it is in the harness, I did not see any structure that would equate to it. Each pair of wires in the harness goes to a solenoid with the exception of the six-wire connector that goes to the position range sensor. If you look at the picture of the harness, there are no pairs of wires the have a third wire, which would be needed to carry back the signal from the thermistor.

It appears the temp sensor is inside the trans range position sensor, but I can't really confirm that. I believe the 8-cylinder application transmissions have the thermistor in the harness; I can't see one in my GM six cylinder transmission.

Attached is the schematic for the six cylinder tranny. It appears to show the oil temp sensor as part of the range position sensor-I think. Can anyone verify where X8505 is physically? Is it part of the range selector sensor? The colors labelled on the schematic to not fully correspond the colors of the actual harness.

I did purchase my replacement harness from ECS Tuning, and on their website it does say replacing this harness will "restore a non-functioning trans oil temp sensor," or words to that effect, but it may be language that carried over from their listing for the 8-cylinder harness.

My schematic is out of a Bently manual for X5s, page ELE-370.

Update:
Ok, I was ruminating at work today about swapping out TCMs, and going against the advice of a trusted friend who happens to own his own INDY shop, when I got home I grabbed the TCM that was matched up with my original, non-operational transmission. After looking at a number of posts on here and other BMW forums with respect to having to reprogram them, I felt pretty confident that if my TCM part numbers and other identifiers matched up, it should work. In the picture with the two TCMs, the left one is from the bad tranny and the lower one is matched to the one I just installed. Numbers looked good. So I pulled my cowl apart, and got into the e-box. Pulled out the TCM, and before I put in the replacement, looked down into the cavities to inspect the pins.

If you recall in my prior posts, I had already replaced the harness from the TCM out to the o2 sensors and down to the transmission. What I did not do at that time was inspect the pins on the TCM; I just left it in place as I swapped harnesses. As you can see from my two additional pictures, I have a pin going "sideways" instead of "up."

Instead of messing with trying to straighten the pin at that time, I went ahead and put my old TCM in anyway. Fired it up, took it for a ten mile run. So far, no MIL, no Rollover mitigation/4x4, light, no "trans failsafe program" warning. It did reach operating temperature, which is usually where I'd get a all the warnings to activate.

I will take it on a longer run tonight and report back.

Good to hear that you might have fixed the problem. So the tcm from the rollover X had a bent pin.

On another trans problem post I informed the poster to look at the connection at the tcm and cable.

http://http://www.xoutpost.com/1069110-post8.html