2015 8L90E swapped into a Square Suburban, factory TCM, have never been able to complete a fast relearn.... been running it now for 2 years and nearly 30k miles, its been trouble free, but boy does it have some shift quality issues.... I figured after 2 years id try the fast learn again with the latest VCM update to see..... same results. monitor "Trans fast relearn status", temps over 167, start the function, pid says shift to D, shift it to D, pid changes to "Purging", you can feel 8 light pluses and sounds, pid changes to "Calibrating D", but from here on out, zero sounds or feels, and after 6 or so minutes it changes the pid to "Abort". I've tried several times, no codes in TCM. tired with a Snap On scanner as well, same result, it shows error and aborts. Any input would be appreciated, attached the trans file.
side notes.
-no BCM.
-no Gen 5 ecm.
-its driven with a PCS canbus interface to simulate the Gen 5 inputs. I have the abilities to change many factors for inputs, but non seem to affect the learning abilities.
-was a brand new GM crate trans, has a Yank 2800 triple disk, stock 2015 TCM from wreckers, Dealer friend flashed in the PUN/TUN data when initially installed, as stated, it works well, just has wildly harsh, hot reverse engagement and intermittent 3-2, 2-1 harsh downshifts (like 90% of stock gm trucks).
Happy to report that I was able to complete the fast learn, I watched some other folks who videoed the process, and realized the engine revs during parts of the test, and due to my engine not being on the Can Bus, I had to add the throttle input, I held it around 1000 rpm, and after the purge process, the main calibration was able to complete! and now my reverse is silky smooth!
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