First time posting in a few years. I built a motor for my 88 K5 4x4. Nothing crazy, just a 350 ZZ3 with Torquer heads, roller cam, 20 PSI. All designed for low rpm torque. With the mods, I had to do a custom chip. 747 with EEProm conversion programmed with TP and AutoProm USB. Never became anything like an expert, just learned what I needed (pretty minimum) and got it going. Everything has been just fine for a few years, and my daughter has been using it for her convenience since she started driving a year ago. It's been passing smog tests with flying colors, running good... So much for history, now for recent events. She tells me she saw the SES a few times, so I figure probably a sensor, maybe a wire. Had her pull it into the shade and it smells a little rich, and doesn't sound quite "right". Hooked up the AP today and couldn't get it to pull the code through ALDL. Fired it up and started getting raw data, but only some rows. Lots of stuff, like O2, I'm getting nothing. Most tables have no data. Switch to TP and "dash" shows nothing. Switch to emulation and nothing works. After some more fiddling around, I realize that it runs the same with or without the chip in the socket. So now I'm thinking the ECM might be bad, but short of scrounging up one and running a stock PROM long enough to see if I can get data, I haven't the foggiest idea how to proceed. Anyone got some advice? Maybe I just forgot something important about configuring/using this thing??? Any help would be much appreciated.

It could be a PROM failure, doesnt have to be the PCM, sounds like its still working correctly otherwise, its running off the cal-pak, that's for sure.

Do you still have the tune saved, could you just get a new chip, burn your bin and see how it does, or like you said just get a stock chip just to see if that fixes the problem and you have to re-tune.

Do you still have the chip burner, if so can you read the one in there now or is that ****ed too?

I do still have the AutoProm and the final bin file used. I loaded it into TP, then did a "verify" against the chip. TP says it is identical. I have a spare/extra chip, so I will program it tomorrow and see what happens. With not being able to read anything from ALDL, or in emulation mode, I don't expect it will help. I used to have a spare ECM in my rock crawler buggy, but I sold it, and now have nothing to swap.

I still haven't tried a different chip, but given that TP "verify" said it was identical to the saved bin, I don't have much hope that it will help. Still, I'll try tonight...

I've been sniffing around for an ECM that I can use to at least verify that swapping the ECM does let me get proper ALDL data. And if so, to form the basis for a newly modded ECM to place my ROM into. Short of going to a salvage yard, no luck yet.

But I did find a friend who has a 7748. Any idea how this will compare to a 7747? Will it run well enough to test the ALDL logging? Will it be acceptable as a base to mod for my ROM? Never heard of a 7748, and my friend doesn't remember where he got it...

Oh well, I found this thread (OK I'm really confused now) that indicates 7748 needs a different mask, which means at the very least, a different "program".

I would suspect a bad pin connection between the chip, socket, and ECM.
Check your solder joints for continuity. One may be loose.