4.6iS Torque Converter
 

Anyone familiar with the notorious 4.6iS torque converter issues? I started getting the TC error a few months ago and I could clear it and would come back a few weeks later but it will now pop back up either the same day it's cleared and driven or possibly the next day. The trans shifts flawlessly and I couldn't tell you there is any performance issues I could notice. I do have a rebuilt 4.6iS TC ready to go so it doesn't sit on the lift more than a day along with real crank seal, rear coolant cover gasket, torque converter seal and new exhaust bolts. Any other experience or recommendations I can use?https://uploads.tapatalk-cdn.com/202...2de8284043.jpg

1. How old is your fluid and are your trans cooler/t-stat operating properly?
2. Is the trans fluid at the correct level?
3. No vehicle speed is shown on the INPA readout, this would be helpful in determining whether the issue is likely fluid related or clutch related.

It seems at the time of the fault your fluid temp is perfect but if it has been overheated before it could have lost viscosity. Please take what I say with a grain of salt because the auto driveline is my weakest point when it comes to automotive knowledge. I'm going off theoretical (book) knowledge not first hand experience when it comes to autos.

The error popped up on 8.20.2020. The Trans fluid and filter has been changed since then on 9.2.2020 which appeared to be the first time it was ever done. The trans shifts buttery smooth and had Dinan software but I still get the TC error most often. A friend with experience with 4.6s says the only way to properly get rid of the error is to swap the TC which he has had to do on the many 4.6s he has owned as it is a common failure point...https://uploads.tapatalk-cdn.com/202...7137d7405d.jpghttps://uploads.tapatalk-cdn.com/202...eab3694e82.jpg

Like I said most of my knowledge on the subject is based on books. That said, any torque converter basically has 3 failure points:
1. The stator or impeller blades or turbine blades self destruct which is a catastrophic failure and your car will go nowhere.
2. The clutch fails to lockup, in this case the car will drive but your MPGs will decrease noticeable as well as the cruising behavior.
3. Or the fluid is out of spec either in volume, temperature, or viscosity.

#1 most certainly require a replacement and since you're vehicle is still mobile this can be ruled out.
#2 could be an electronic issue if the lockup is electronically controlled, which on the 4.6is it is. Replacing the electronics in this system is a hell of a lot cheaper and less labor intensive than replacing the converter so it is recommended that the time be taken to properly diagnose the root cause of the issue.
#3 is self explanatory and as long as the fluid change was done properly with the trans being warmed up, shifted, driven, and level checked/topped off then this has been ruled out as well.

Check out this thread:

https://xoutpost.com/bmw-sav-forums/...stuck-off.html