4l80 lockup issues attached current tune
TECH Fanatic
Joined: Jul 2010
Posts: 1,756
Likes: 4
From: Maryland
Had the same problem on my stock 2001 Suburban 2500 with a 4L80E. It would lock up at 50 and disengage at 65 and never go back into lockup until coming to a stop again, however it could be commanded on/off just as you are describing. I deactivted P0300 to no avail.
You may have to do the same thing I did and to into the misfire code parameters (time between misfires) for the mid rpm range while driving. I left the idle parameters alone. Once I opened up these parameters (I set them to the max of 32,500 for testing) and it went into lockup no problem.
I'd reset everything else you've been told to change and try to open the misfire DTC parameters.
You may have to do the same thing I did and to into the misfire code parameters (time between misfires) for the mid rpm range while driving. I left the idle parameters alone. Once I opened up these parameters (I set them to the max of 32,500 for testing) and it went into lockup no problem.
I'd reset everything else you've been told to change and try to open the misfire DTC parameters.
