Background: I am in Nevada, USA (pacific time zone). I bought an 04 Avalanche 2500 with the 8.1 and the 4l85 trans. I *think* this is the LS1B ECM(?) The previous owner lifted it, slapped 35's on it and regeared to 4.56 front/rear. He used a Hypertech to adjust the shift points and account for the gear ratio/tire size.

I have a flash scan v2 I bought years ago when I had a previous truck tuned, so I grabbed some data logs. Then I realized, the Hypertech probably pulled bunk data so it would be best to de-tune with the hypertech before getting good logs for EFILive tuning.

I went to uninstall the hypertech tune and it failed to re-write the stock tune multiple times, giving code 8E and saying to call hypertech (they are closed weekends). The truck won't start now, and is parked on the street in front of my house. I don't really want to pay a tow truck to take it to the dealer if this is a simple procedure I can do with this device I have already paid for.

I pulled out my old computer, updated the EFILive software, the Flash Scan Firmware, bought a new VIN license and tried to read the tune that is on the truck. The result shows there is an invalid checksum in speedometer segment 8. I don't know where that is, or how to fix it. I exported the speedometer data into a CSZ file(?) but it looks like gibberish in notepad and I wouldn't know how to save it anyways.

Instead, I tried to modify some of the speedometer values that seemed waaaaay out of range (e.g. tire size = 11138.84"). I compared the data to some old tune info, and some files I found here, but the PCM wouldn't take my tune.

I've searched and read, and I feel like I'm fairly close to getting this resolved, especially if I can get a good stock file and change the VIN to match mine, or if I can read what this segment value is and modify it to something that works. I've read that there might be more in-depth solutions like updating the OS to the newer version and copying over my engine data, but this is really the first time I've done anything other than move tunes around from email to the truck.

Any assistance would be helpful, and I appreciate the time you took to read this post.

(I will have to post a few more times before I can upload files, I think)