Okay, I've got an l83/6l80e supposedly from a 2016 Silverado in a 1988 in a K5 blazer. It ran when purchased. Day one I went to clean up the rat's nest/fire trap and like an idiot didn't disconnect the battery and direct shorted a 12v cable. Hasn't started since. Corrective actions were I pulled out the janky OEM mess that was crammed in the truck. Swapped in a stand-alone harness. Ensured I had 12v to all my factory lines that should. Hooked up any loose engine grounds I could find. Took my time straightening things out while I waited on the new harness. Followed the directions on the new harness and it seems to have the OBDII port wired correctly. I've got 12v to the port, 2 grounds, and the canbus lines are there. Now, whenever I hood my pro cable up I get a "detect protocol error." Connects fine to my wifes car. So, I suspected maybe the ECM was toast, and ordered a new one, didn't think about it being blank and needing programmed at the dealer, but it gets the same error.

I haven't made it to the dealer to get the new one programmed, but is that an expected error, or should it still be able to connect and at least detect it? All of my other prior experience was with gen III motors. I know the gen V is a significant change from those. A quick google shows noise on the system and resync interface. Resync doesn't fix anything. Since it can connect to my wife's car it doesn't seem like an mpvi cable issue.

DLC pins 6&14 had 120 ohms, I added a 120ohm resistor across them and I now have 60 ohms.

Google showed speartech having people double check the trans harness to ensure it's plugged in. Unplugged and plugged back in looks fully seated no wiggle.

Harness is from highperformanceinjectors. Anyone else run into similar issues and have any troubleshooting tips?

 

A dealership most likely wont be able to flash the ecm in your swap. If they were able to flash it, its still not going to run until its programmed for a swap which the dealer cant do. A new ecm even blank you can connect to.

 

Thanks for the info that ECM even if blank should still be able to connect. I have HPtuners Pro, but I've only ever dealt with gen III swaps before. So this is my first gen V interaction.

I've got a modified stock base tune off the repository that I've went through and disabled VATs, starter diag, rear O2, fpcm, ran tire calibration, a litany of evap codes. I just hate to dump another $100-150 on them to flash stock 5.3 4wd with the VIN from the file I've got if that's not the problem.

I need to try the new/blank ECM again since I've put the 120 ohm resistor at the DCL. If it can connect in any manor then I know it was the old ecm. If not then it's more harness troubleshooting. I guess?