8l90e help needed (tun programming)

Finished putting a 2018 LT4 into a 1970 Camaro with a 8 speed (8L90E)

Engine harness, ecu, tcm was purchased from PSI conversions. Transmission is from a 2016 silverado that is converted from 4wd to 2wd.

Finished the swap and drove the car, drives decent, all 8 gears work, but the transmission shifts clunky and seems very confused. Sometimes it gets stuck in gear or slips into neutral. Bang Shifts too.

The only codes we are have all the p27 codes.

P27A7, P27AA, P27AB, P27AC, P27AD

No other codes. I suspect these codes are related to the TUN / PUN number not being calibrated into the TCM, so I had the ECM and TCM sent back to PSI for them to program the TUN number into the TCM and they said they did it and mailed it back. However when I got the ECU back these codes are still here.

What are my options now? I spoke to the tuner at PSI and he said he entered the TUN number... I have no reason to not trust them.

I cannot do a fast learn on the transmission because codes are present. I cannot tune the ecm with HP tuners because its locked, and having them unlock it will probably remove the TUN programming info that PSI entered into the TCM, in which case it would have to go back to PSI for that to be entered again. (2 week delay)

GM dealership cannot program TUN number into the TCM because the vins do not match or the vehicle doesn't have a body control module which MDI2 needs to see to verify some programming information.

Any tips? What can I do to rectify these codes?

Would swapping in an early (2016) t87 tcm from a 2016 silverado be a smart thing to try because that would match the transmission better? Trans is a 2016 silverado 8 speed.

Quote:

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Originally Posted by Highlex

Finished putting a 2018 LT4 into a 1970 Camaro with a 8 speed (8L90E)

Engine harness, ecu, tcm was purchased from PSI conversions. Transmission is from a 2016 silverado that is converted from 4wd to 2wd.

Finished the swap and drove the car, drives decent, all 8 gears work, but the transmission shifts clunky and seems very confused. Sometimes it gets stuck in gear or slips into neutral. Bang Shifts too.

The only codes we are have all the p27 codes.

P27A7, P27AA, P27AB, P27AC, P27AD

No other codes. I suspect these codes are related to the TUN / PUN number not being calibrated into the TCM, so I had the ECM and TCM sent back to PSI for them to program the TUN number into the TCM and they said they did it and mailed it back. However when I got the ECU back these codes are still here.

What are my options now? I spoke to the tuner at PSI and he said he entered the TUN number... I have no reason to not trust them.

I cannot do a fast learn on the transmission because codes are present. I cannot tune the ecm with HP tuners because its locked, and having them unlock it will probably remove the TUN programming info that PSI entered into the TCM, in which case it would have to go back to PSI for that to be entered again. (2 week delay)

GM dealership cannot program TUN number into the TCM because the vins do not match or the vehicle doesn't have a body control module which MDI2 needs to see to verify some programming information.

Any tips? What can I do to rectify these codes?

Would swapping in an early (2016) t87 tcm from a 2016 silverado be a smart thing to try because that would match the transmission better? Trans is a 2016 silverado 8 speed.

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You should have the TUN on the right side of the transmission. You can check that with the numbers on the programming, or the dealer can. I work for a GM dealer. do it all the time for a local speed shop. VINS dont need to match to program. You can just use the VIN for the engine and trans that came out of what you got them from. May possibly need to remove the trans pan and get the PUN for the valve body. Sometimes you have to program it separately. Those codes only set from calibration of the solenoids not being learned. Which makes me wonder if the valve body is different.

In regards to this I have a 8l90 that the TUN sticker was wiped clean after a rebuild. This was a trans from another vehicle 2016 camaro installing in a 2017 camaro, I had the valve body replaced I updated the PUN in GM TLC SPS. TLC takes the update it seems, but when I tried to do a fast learn it has failed multiple times. I pulled the pan to verify the PUN again it is correct.

Fluid at correct level, temp of the trans 167 degrees when starting the Fast Learn. I even just tried running the car on the lift and had no shifting other than 1st/2nd then it will kick it self back to 1st. (with traction control off of course). I was thinking at first it might of had something to do with IMS switch indication as there were the 4pin and 10pin, this has the more common 10pin switch. I don't know if there is a way to figure out the TUN from the 16 car the trans came from, the only thing I have is the VIN from that car now. But I wouldn't think that would matter being I have the PUN and between the valvebody, IMS and wiring harnesses I don't see anything that would make the TUN matter. I tried to put a random TUN in from another car with my correct PUN and got nothing again. Being it appears the solenoids are not firing I can only think it has something to do with the TCM not properly programmed or a wiring harness issue / valvebody (NEW from GM) issue.

The car is just being put back together from being a stripped repo. It has all the original modules in the car except it has a different E92a ECM as when I got the car it didnt have a ECM. The motor is from the same 2016 car, we had to switch the engine harness over to a 17 along with the fuel rail harness and fuel pressure switch. The car has the orgional T87a TCM in it just unlocked by HP. I also have a T87 from the 16 car but I couldn't update the PUN in TLC so I sent the T87a to be unlocked
I do have indication from the IMS switch for Park, Neutral, Reverse, when I go to drive it says UNKNOWN 82.
I have a J2534 cable to connect to Techline but have very limited experience with it.

I am somewhat at a loss to get this thing working but I feel like I am missing something stupid or not doing something right.