Okay, I have everything repinned and ready to run with my 91 harness swapped into my 87. The way I understand it, through the GM wiring diagrams, VATS sends a signal to the ECM for fuel control, meaning the VATS module grounds terminal B6 on the ECM to tell the ECM everything is green to go.

Right now, as she sits, I have a code 43 (my knock sensor has been there for a while with nothing connected to it so I figured this one might pop up) and a code 46 (VATS signal out of spec). I can crank her over all day and I might get a slight hiccup, but no vroom. I'm guessing that just switching the B6 to ground (through the DKBLU wire at C207) isn't what the ECM is looking for. Anyone have any insight? I need to know so I can make it to work in the morning!

 

you are just a little off. and run "SEARCH" under vats and you will find a lot of stuff on it.
here is what happens. you turn on the key and charge the system. the ecm looks into its internal programing and says - Im supposed to look for a vats. so it sends a signal to the vats. the vats then sends a signal up the steering column and asks the reader to check the resistence on the key. the key reader sends down the data and the vats says yes or no and tells the ecm.
the default is always IMPROPER VATS. so if you pull the wires, dont have a reader, take the vats out, the default is HELP IM BEING STOLEN - SHUT DOWN.
do you get a flash on the check engine light when you turn the car on?
is the vats module you have the same one that was in the car all this time or did you change it? the module is looking for a specific key and if you put in a module taken from the 91 it probably will not recognize your key as the proper one.
put the old vats back in and check it again - the ecm does not care what year vats your car came out of - it sends the same signal all the time.
or - is the key reader in your car bad?
that is a start.
https://www.thirdgen.org/forums/elec...able-vats.html is one site devoted to the topic.

 

My car is NOT a 91... It's an 87, meaning NO VATS system. I wasn't planning on pulling the entire wiring harness from the donor car just to get this thing going the way it should. It seems that all I need to do is duplicate the VATS signal to the ECM, which I am assuming is some sort of frequency signal, similar to Chrysler and Ford MAP sensors (but using a standard crystal, of course)...

:edit: I found what I was looking for, finally. Here, for others who might want to know:

http://www.fastfieros.com/tech/gm_vats_passkey.htm

The ECM requires a 50Hz signal at terminal B6 for Fuel Enable... Now I just have to get a matching crystal.

 

First is the VATS system was the fault your car would NOT turn over VATS kills the starter... I would check your fuel pressure and your oil pressure switch (it controls your fuel pump) Your should get when you turn your key a 30 sec prime.... then when your cranking your pump should turn on again. If not you will need to bypass that switch by crossing the two outside wires your pump should start running until your disconnect the wires. (mine has a switch in there for hidden kill switch)
If your getting what your calling a hickup when cranking I am guessing your getting spark just no real fuel pressure.... if you are getting good fuel pressure and spark but still not starting I would look in another direction then VATS

Oh yea there is no frequency signal for VATS ............. VATS is a resistance that it reads from the key chip and then if it matches the VATS box then it will engage the relay and enable your starter

 

yes but they have to communicate and its by a signal, weather the signal sends the resistance or something else that says what the reader finds the resistance to be - there is a signal. the vats mod either agrees that this is the correct chip in the key and the vats mod will agree or not agree then the vats sends a signal to the ecm.
if he has a ecm that is programed to look for a vats and a vats module isn't there, the default is improper vats signal and it will not run.
so since he does not have a vats key reader talking to the vas module, having the vats module does him no good at all, except as a convenient place to put this radio shack resistance chip wires.
but electronic devices talk to each other with electical signals and those signals can convey any information that they are designed to convey, even if its only a resistance level or turns a bit on or off.
either short the vats with the site i gave you - i think its better than the general one you have - or get a new chip burned without the program asking for a vats.
if you look down on the link i provided you will get actual photo's of what you need to do and the various resistor values.
burning a new chip is always best.

 

Right but like I said it will also not allow the car to crank and seeing he is transplanting wireing harness we dont know for sure what all is there modified or connected that would keep the system from working.

 

Never mind about the VATS problem.... About 11:30 last night I remembered that I have a spare PCM in my garage that I was planning on using with my 93 Grand Prix (with the LH0 3.1, FWD) that didn't work and I was going to throw out. I went and found it, and now I have a non-VATS MEMCAL in the Bird.

Now, if I could just figure out that code 43 and why the engine runs like garbage unless I have the EST bypass disconnected, I'd be all set.

BTW, the 3.1 harness is unmolested with the exception of repining a couple of things in the main C100 connector to match up with the existing dash harness and the replacement of the 3.1 fuel and fan relays with the 2.8 ones. I don't even have my wiper motor hooked up at the moment, as I am looking to get the one from the donor car tomorrow.