Hi all

I have a 2003 Duramax LB7, original owner so I know the ECM hasn't been touched by any previous programmers and I can't recall the dealer ever having touched it either. About 3 months ago I started working with a diesel performance shop in the pacific NW, they read out and saved my stock tune, saved the .ctz file and emailed me a copy as well. Then they installed a DSP5 tune set from a well known tuner with Flashscan V2 version 8.02.21. Fast forward to today, we are debugging a driveability issue and wanted to flash the ECM back to stock to create a baseline. Today they tried to flash my ECM back to the stock tune that was previously read out, and the truck would crank w/o starting, security light on the dash. Sure enough when we put it on the bench and read with Efilive, the VIN number was incorrect. It wasn't all zeros like the 01/02 ECMs seemed to be prone to doing, but something like mostly zero with only the last 6 digits containing a number.

We're at a loss, he assumed the original tune he had saved was possibly corrupted somehow and suggested programming a clean stock 03 image back into the unit. What is the recommended course of action to proceed to get this ECM back to stock with the correct VIN?

I took a look at the .ctz file and the text headers did contain valid S/N and correct VIN. (I removed some of the actual digits with xxxx) Is there any way to verify validity of a .ctz file and confirm the theory that the stock tune read out of the ECM 3 months ago was somehow corrupted?

Binary=UPLOAD
Software=V8.02.21.404
Bootblock=V2.07.08
BootblockDate=20180704
Firmware=V2.07.138
FirmwareDate=20181025
BootLoader=DLB7_v1.3R
ObjVer=08.04.73
ObjDate=20180515
...

[VEHICLE],19
Stream=E54
StreamID=4
VIN=1GCJK39103E33xxxx
SN=3128CT08xxxx
OS=15189044
BB=0
CVN=$0
CodeVer=0
CodePart=
BootVer=0
BootPart=
PartNumber=0
Code=
ProductID=
Name=
COSOnly=0
SDMKey=0
ManufactId=
Custom=0
[SEGMENTS],11
S00=15189044
S01=15189052
S02=15076379
S03=15076354
S04=15076385
S05=15076392
S06=00000000
S07=00000000
S08=00000000
S09=00000000
S10=11463752
[SECURITY],21
Read=1
Modify=1
AutoLock=0
Serial=0
License=0
Remote=0
Master=0
SN=0
Password=0
Checksum=1
CalFlashOnly=0
FullFlashOnly=0
OverrideOS=0
RemoteKey=
RemoteKeyFrom=
RemoteKeyTo=
TryAltKeys=0
AssumeLockFaulty=0
LowSpeed=0
CMFastCan=0
VIN=0
[INFO],4
CalibratedBy=.
ModifiedBy=.
Created=20190219
Modified=20190219
...binary stuff follows