OS swap issues

[Pusher]

I loaded an 02 OS into my 99 silverado, and the battery light in the message center started coming on for a few seconds and going back off, over and over. So I tried an 01 OS, and got the same result. My battery and alternator check out OK. I guess I'll go back outside now and try my stock OS and see what happens.

[Pusher]

Well, that fixed the battery light. I have read about upgrading the OS on the 99's before, but never saw anything about this problem. It looks like if the tune had anything to do with it, I would be able to fix it in the tune, but apparently the tune was the culprit and I have no idea why!

[joecar]

Pusher, welcome to the forum...

Only certain OS's go into certain PCM's... that may have been the problem... I don't know which ones.

What OS's are involved here...?

[Pusher]

My stock OS= 09373372
The 02 OS= 12212156
The 01 OS= 12208322

[GMPX]

Did the 99 run the same alternator as the 02 did?
If they are different this is where the problem will be.

Cheers,
Ross

[dc_justin]

Well, that fixed the battery light. I have read about upgrading the OS on the 99's before, but never saw anything about this problem. It looks like if the tune had anything to do with it, I would be able to fix it in the tune, but apparently the tune was the culprit and I have no idea why!

Compare the Generator L and F terminal DTCs in the 99 OS to the 02 OS. You need to disable one of the two of them in the 02 OS to run on your 99 (I forget which off the top of my head).

[Pusher]

Ah, I see the difference now The F terminal circuit is not reported in my stock tune. Thanks a million guys, all the help that's available on the forums is what makes EFILive so great.

[joecar]

Cool......I learn something here all the time...