6l80e with tap shift no BCM

[92GreenGT]

Hey guys, been searching and ran across this thread. Going to be looking into doing this as well on getting the TUTD shifting to work in a 98ish Silverado with a LSA 6.2/6L90e config that has a Lokar shifter with the Tapshift wired into pin 7 but it?s ECU is a LSA e67/tcu t43 and no BCM. It?s not looking good from what I?m reading on getting this exact combo to work with the TUTD mode. I was ready to try a segment swap on the trans from a corvette tune until I read the last post about the TCU known to brick if trying to write a 6L80e segment over it. Lol. So I want to do some more reading/investigating before I pull the trigger on anything just yet. Just replying to this thread to keep easier track of it mainly. Thanks

[Rynoknows]

I am hoping someone out there can tell me what the heck I am doing wrong. I bought this Jeep and the guy told me that it was all set up for TUTD. I have completely checked and redone everything I can find on the internet. Can't get it to go into TUTD mode. I have a attached the first read I did.

I saw this list of questions earlier, so I figured I would answer them for my build.

What engine and transmission are you using? 2017 Silverado 5.3, 6L80 trans
What OS for engine/transmission? E92A, ECM, GM SIDI 2017+, OS-12677878 and T43, TCM, GM A6, OS-24276638
What vehicle did it go in? 2017 Silverado 5.3
BCM? no
What shifter are you using? modified Winters 4L60
What shift quadrants do you have? PRND, PRND,D4,3,2,1 etc... I have P,R,N,4(D6),3(D4)
Did you make your own switch wiring or buy a setup? it came with the shifter
What is the switch wired to? toggle switch for activation and momentary switches for TUTD wired into Winters shifter
Pulling the connector on the transmission, is TUTD wire in pin 7? yes
What does it do? Whenl i run the scanner, I can see when I pull the shifter down into 3 it appears as D4. When I toggle the power on (simulating putting it in Sport Mode) and move the shifter from side to side (activating TU signal, TD signal) it will not go into TUTD mode.

[AlanDC]

I am hoping someone out there can tell me what the heck I am doing wrong. I bought this Jeep and the guy told me that it was all set up for TUTD. I have completely checked and redone everything I can find on the internet. Can't get it to go into TUTD mode. I have a attached the first read I did.

I saw this list of questions earlier, so I figured I would answer them for my build.

What engine and transmission are you using? 2017 Silverado 5.3, 6L80 trans
What OS for engine/transmission? E92A, ECM, GM SIDI 2017+, OS-12677878 and T43, TCM, GM A6, OS-24276638
What vehicle did it go in? 2017 Silverado 5.3
BCM? no
What shifter are you using? modified Winters 4L60
What shift quadrants do you have? PRND, PRND,D4,3,2,1 etc... I have P,R,N,4(D6),3(D4)
Did you make your own switch wiring or buy a setup? it came with the shifter
What is the switch wired to? toggle switch for activation and momentary switches for TUTD wired into Winters shifter
Pulling the connector on the transmission, is TUTD wire in pin 7? yes
What does it do? Whenl i run the scanner, I can see when I pull the shifter down into 3 it appears as D4. When I toggle the power on (simulating putting it in Sport Mode) and move the shifter from side to side (activating TU signal, TD signal) it will not go into TUTD mode.

Basic questions. Is the engine spinning and transmission too? Is trans fluid level ok? I have the exact same engine and trans with TUTD enabled. But just can bus driven. Not hardwired.

I've also worked on similar setups for customers with hardwired tutd option.

[Rynoknows]

Alan, thanks for responding so fast! Yes, engine a transmission all seem to work fine. All fluid levels great. This rockcrawler has really low gears and it seem to shift through the gears very fast in drive and lug the motor a lot. That's why I wanted to try and get the tap shift working especially when crawling trails.

[AlanDC]

Alan, thanks for responding so fast! Yes, engine a transmission all seem to work fine. All fluid levels great. This rockcrawler has really low gears and it seem to shift through the gears very fast in drive and lug the motor a lot. That's why I wanted to try and get the tap shift working especially when crawling trails.

Resistors are working ok? Did you double checked the ohm values???

[Rynoknows]

Ya, I double and triple checked and then bought new resistors and built a complete new one. Neither of them made it work. I am going to go through it top to bottom one more time tomorrow.

I have written and re-written to the TCM. Once I write it and it finishes, is there anything else I need to do? I have been at this off and on for 2 months. Is there anything to when it is in drive it shifts really early and really lugs the motor? This is my first venture into all this fancy new stuff.IMG_0610.jpg

[AlanDC]

Ya, I double and triple checked and then bought new resistors and built a complete new one. Neither of them made it work. I am going to go through it top to bottom one more time tomorrow.

I have written and re-written to the TCM. Once I write it and it finishes, is there anything else I need to do? I have been at this off and on for 2 months. Is there anything to when it is in drive it shifts really early and really lugs the motor? This is my first venture into all this fancy new stuff.IMG_0610.jpg

Set comm codes U0121 and U0140 to not report. Also keep in mind that the TUTD mode will activate when you have the shifter in the desired position as programmed and you press the up or down shift button in your setup.

[Rynoknows]

Yes, I believe I have the codes set correctly. My tune is listed in the above thread. I am aware you have to first give it the signal through the 8k resistor to tell it is in TUTD and then you actually have to make a shift (pull the lever so it goes through both 8k and one of the other resistors in parallel) I have confirmed that when I give it the signal (power) it shows 8.23. I move the shifter side to side and I have 2.87 and 1.26 respectively for up and down shifting. I measured this from the point in which I apply power at the shifter, to the #7 pin on the connector at the transmission. It sure appears that it seats properly into the transmission plug connector. Is there a way to test the TCM or see the input on HP?

I compared the tune that is in the Jeep to a stock tune I found and it appears that someone has changed more than the basic things that are associated with this mod. I have been contemplating loading a stock tune from this other file on HP and starting over from scratch. I have confirmed that they are the same T43 and the same OS. Am I going down the wrong path? It is either that or order a new TCM?

Switch wiring.JPG

[AlanDC]

Yes, I believe I have the codes set correctly. My tune is listed in the above thread. I am aware you have to first give it the signal through the 8k resistor to tell it is in TUTD and then you actually have to make a shift (pull the lever so it goes through both 8k and one of the other resistors in parallel) I have confirmed that when I give it the signal (power) it shows 8.23. I move the shifter side to side and I have 2.87 and 1.26 respectively for up and down shifting. I measured this from the point in which I apply power at the shifter, to the #7 pin on the connector at the transmission. It sure appears that it seats properly into the transmission plug connector. Is there a way to test the TCM or see the input on HP?

I compared the tune that is in the Jeep to a stock tune I found and it appears that someone has changed more than the basic things that are associated with this mod. I have been contemplating loading a stock tune from this other file on HP and starting over from scratch. I have confirmed that they are the same T43 and the same OS. Am I going down the wrong path? It is either that or order a new TCM?

Switch wiring.JPG

Send me a PM I try to help you out. We'll exchange info by email or phone. Will be easier for me.

[Rynoknows]

Hey Forum!

I always get frustrated when people don't come back and post a follow up to what happened and if they got it working. Short story, I GOT IT WORKING!! LOL

I am not exactly sure what the final thing was but I took the tune completely back to stock and started over again. I used all the info from this forum and the settings from "Beehive's posts". The other thing I did was I wrote "write Entire" not just "write calibration". not sure if that did anything but it was a step.

A couple of lessons I learned along the way:

Make sure to disable the trouble codes
Make sure the plug is completely seated in the transmission
The resistors can be a little confusing but if you understand basic electrical circuits it actually measures DC current flow in the TCM
Understand what setting your shifter/transmission needs to be in to make it work D6/D4 or whatever. It was really well described in the YouTube video. https://youtu.be/34u5nH06x6Y

Special thanks to AlanDC for helping me go through everything to double check!

If there is ever anyone I can help, please let me know. I would love to pay it forward!

[Butcha225]

Seems I have found a different problem with this TUTD function.

I have correct wiring and resistance. VCM scanner with show TUTD in 'Trans Shift Mode'.

The issue is TUTD mode will on run for around 60 seconds then change back to 'normal'. TUTD will not work after. I unplug the trans connector then plug it back in and TUTD will work again, for 60 seconds.

Has anyone else had this issue?

6.2 LSA E67, ECM, GM Gen4 12656942
6L80e T43, TCM, GM A6

[AlanDC]

Seems I have found a different problem with this TUTD function.

I have correct wiring and resistance. VCM scanner with show TUTD in 'Trans Shift Mode'.

The issue is TUTD mode will on run for around 60 seconds then change back to 'normal'. TUTD will not work after. I unplug the trans connector then plug it back in and TUTD will work again, for 60 seconds.

Has anyone else had this issue?

6.2 LSA E67, ECM, GM Gen4 12656942
6L80e T43, TCM, GM A6

Wich OS do you have in the T43? also, will be a lot easier to check if you post your complete tune file and scanner log.

[Butcha225]

Wich OS do you have in the T43? also, will be a lot easier to check if you post your complete tune file and scanner log.

Hi AlanDC,
FIles attached below.


Screenshot 2025-06-09 120333.jpg
A1BOSS_TapShift_70Idle.hpt
tap3.hpl

[Izzy c10]

this might be weird but I've made a tap shift harness before and from where you tap the 8.25k resistor into the "TO TRANS" i get the reading on one side and not out the other end on the 8.25k resistor what was i doing wrong?

[AlanDC]

Hi AlanDC,
FIles attached below.


Screenshot 2025-06-09 120333.jpg
A1BOSS_TapShift_70Idle.hpt
tap3.hpl

I would suggest you go over the trans calibration part 1 PID at a time and test it. in the log, I saw it stays in TUTD and went to normal when you moved the trans range selector lever. Also, you commanded TUTD by selecting D5 but you?re not getting mph, that?s another test you?d need to run.
Try different configurations over the TCM calibration and do some testing. Not every OS behaves the same.

[AlanDC]

this might be weird but I've made a tap shift harness before and from where you tap the 8.25k resistor into the "TO TRANS" i get the reading on one side and not out the other end on the 8.25k resistor what was i doing wrong?

If you?re following this diagram, you need to check the resistance between the 12V upper lead and the "to the trans" lower lead.

Switch wiring.JPG

[Butcha225]

Thanks For the reply AlanDC,
I had found what i think was the cause from a P0606 DTC showing in diagnostics. I can now get the TUTD feature to hold. Only issues is now im not getting any gear on command from the tap buttons. Will just stay in 1st gear. Have check tap button on the scan tool and its showing TUTD buttons are working correctly.
Have played with the shift timetables and copied once shown earlier in this thread with no success. Is there somewhere else in the trans I should be looking at?