8l90 swap, t87 questions.

[TruckNorris]

I’m new here please bare with me...

I have a 2016 GMC Sierra that I have a good bit of work done to, it came originally a 6l80 truck. I have swapped the trans out with all supporting parts to an 8l90, for performance purposes only. I have everything in and I’m having issues reading and writing the Tcm with hptuners. When I go to gather info, it tells me it’s an E92 ecm and t87 Tcm and I can read and write ecm just fine, but I can not do anything with the Tcm. I get a failed message with boot loader timed out something along those lines. Now I am under the impression the OS is different between the 6l80 e92 ecm program and the 8l90 e92 program? Can anyone give me some guidance?

[VX L67 Getrag]

You might want to supply the original file of both setups to compare, but I don't think the software in the ECM would cause an issue with bootloader in the TCM.

[TruckNorris]

You might want to supply the original file of both setups to compare, but I don't think the software in the ECM would cause an issue with bootloader in the TCM.

I am going to try another Tcm, I got this one used and is probably muffed up.. I’m hoping that’s the issue.. I’ve been through absolute hell with this swap. Long story short I have 1 engine harness for 2016 5.3/6l80, 2 2017 6.2/8l90 harnesses, and one 2016 5.3/8l90 harness that’s in the truck and as far as I know functioning 100% properly, I’m hoping the Tcm is messed up because if it’s something wiring related I’m gonna punch myself in the face lol the last 2 harnesses were bought brand new from gm.

[ironduke]

8l90 needs to be unlocked to be able to do anything with it using h p t u n e rs.

I do not know of any other way, but I haven't looked into it whatsoever myself..

[VX L67 Getrag]

WOW & it's not that cheap to do either & then even more if you need your VIN programmed to it!

[ironduke]

Little bit of googling and 2016 is supposed to be the T87.. 2017 and up is the T87A and only the A needs to be unlocked??? I have no idea, this is just googling myself..

[TruckNorris]

8l90 needs to be unlocked to be able to do anything with it using h p t u n e rs.

I do not know of any other way, but I haven't looked into it whatsoever myself..

Only the t87a 2017+ need to be unlocked, t87 2015/2016 does not.

[TruckNorris]

WOW & it's not that cheap to do either & then even more if you need your VIN programmed to it!

I’ve got a connection at the local Chevy dealer and if not I’ll buy an mdi2 clone and pay for a subscription and learn to do it myself. I have a couple more TCMs on the way to try, and as far as I know my tuner says the Tcm doesn’t store the vin.

[TruckNorris]

So today I tried another t87 Tcm, and I can read and write that as well.. but it’s a diesel program.. so what I have in my mind, someone correct me if I’m wrong.. I want to write ecm and Tcm with truck vin that has 5.3/8l90 configuration, then truck will throw theft light and I go in with hp tuners and change the vin back to my vin and get rid of the theft light? That’s my plan any ideas?

[VX L67 Getrag]

You can try that, but I don't think it will work as there's normally a security section that needs to be written thats not part of the HPT file(it's in the eeprom) so if you can't get that off your original ECM then it will either need to be re-linked or just disable theft options!