Been playing with the latest v8 and scan/tune v3 for a few weeks now. I started with my stock 1999 Yukon 5.7l vortex that needed the engine rebuilt. I played with tire sizes and such.

I got around to changing the engine about 2 weeks ago, went with a mild cam trick flow heads short tube headers, cat delete y pipe n stock mufflers. Stock bore engine.

I'm up to my 3rd iteration tune, have only messed with shift points and DTC stuff.

The rub came about a week ago, I flashed a tune into the stock l31 ecm and got a no start. Only edited shift points on a proven tune. Then the ecm bricked. I drove a spare to work that day. Got back in to realize it wasn't just a bad load but the ecm wouldn't take any cal upload.

Swapped ecm and used my last license on the same vehicle and downloaded that tune. Drove it for about a week and changed shift points and re flashed it. Came up with vehicle security switched back on in my tune so it wouldn't run. I edited the tune, reflashed it only to have it not taken a flash... Again. Returns a $0281 error. Both ECMs now won't auto detect and show nothing but 0's where there used to be data.

The Yukon is bone stock electrical wise even has the stock radio. I have downloaded tunes with and without the radio fuse being plugged in, mostly with the fuse pulled.

So now I'm trying to clear the security on the third ecm so I can drive it again. I'm afraid to attempt to touch this one with efilive hardware or software. Not sure what my next step is...

Any help is very welcome.