6L90 intermittently gets stuck in 3rd gear at a stop

[pghalcrow]

I've been having an issue when coming to a stop, the transmission fails to shift from 3rd into 1st. I can't seem to determine how or when this happens, but it happens about 5% of the time. When this does happen, I will take off from 3rd and with enough throttle, it will downshift into 2nd. Tune attached for reference.

[blindsquirrel]

Unless the tune file has an intermittent failure (and I don't know what anybody would even look for to find something that's pretty much not possible), a log file showing the thing when it happens will be much more useful.

If digging in and finding which specific trans PIDs in the log aren't responding like they should seems like too much work, think about how much harder it would be if you were remote, and going only by text descriptions of a thing that happens once in a while.

[TransGo Robert]

I've been having an issue when coming to a stop, the transmission fails to shift from 3rd into 1st. I can't seem to determine how or when this happens, but it happens about 5% of the time. When this does happen, I will take off from 3rd and with enough throttle, it will downshift into 2nd. Tune attached for reference.

You'll have to post a log capturing the even and be sure to have all the transmission channels selected. Without that, it is crystal ball diagnostic.

[verlon]

I've been having an issue when coming to a stop, the transmission fails to shift from 3rd into 1st. I can't seem to determine how or when this happens, but it happens about 5% of the time. When this does happen, I will take off from 3rd and with enough throttle, it will downshift into 2nd. Tune attached for reference.

trans.png

[pghalcrow]

Log file attached. Time stamp starting at 1:25 is an example of when it happened.

[TransGo Robert]

Log file attached. Time stamp starting at 1:25 is an example of when it happened.

It is indeed commanding it just like you described. Almost none of the transmission channels were selected for that log, but of those logged everything was identical when it commanded 1st as it should at a standstill vs when it commanded 3rd. I would address what verlon pointed at first, the issue is probably in the tune. If it's not in there, then I would have see what the range sensor switches are reading, what the TUTD switches if present are reading as well as all the solenoid command etc.

[Alvin]

trans.png

Yeah this 100% looks like it.