Sounds like a problem other than the tune write or an additional problem. I would be surprised if that oil light reports back the ECM and isn't just a switch tied directly to the light.
Wondering if you came up with a solution. I an having the same issue with a 99 cavalier. Originally it said the vats were disabled. I changed a couple of the timing settings. Car started and ran fine. Friend trailered it back home 2.5 hrs away and car would start and shut off. Brought it back. Enabled and disabled vats. Changed all the security settings car starts then cuts off. Check codes and it is giving me a U1016 code
Sorry for long delay getting back here -- no solution yet...
Stock tune read attached..
Also, pretty much every light on the dash is on (some come and go, some are always there)... Battery (verified charging is good), oil, brake, ABS, radiator fluid low (checked, its good), theft protection (on solid -- this is why I wrote to the ECU in the first place)...
Pretty much everything EXCEPT check engine...
No codes stored when scanned either...
Engine starts right up -- idles smoothly -- seems to cut, like a rev limiter, at about 2000 RPMs...
One thing I did figure out is that the dash panel IS the BCM AND the SECURITY MODULE...
I am starting to wonder if something bricked out the BCM or something like that...