My 93 would not start the other day. Turning the key does nothing. I jumped the gun and replaced the starter. Nothing. I then replaced the neutral safety switch. Still nothing. When I turn the key to the ON position, I hear the fuel pump, or whatever, under the hood "charge" up (run temporarily) and when I turn the key to start, the only thing I can detect doing anything is I get a kind of relay-type click from a small, black box, about the size of a pack of cigarettes, under the driver's side of the dash above the throttle pedal area. It makes a single "doink" sound (like a flasher makes) when the key is turned, and thats it. There are actually two of these little boxes, but only the one with the serial number starting with 121xxxxx does it (the other one's number starts with 120xxxxx). My parts guy couldn't find anything on this number, and I don't know what it is either. I only mention it cause it is the only thing that does anything when turning the key. However, since it IS doing something, I figure the ignition switch itself is not out, cause it must be sending it power. But, I don't know that it still might be broke, I guess.
After doing all this, I find out about the VATS problem with these cars. I have already checked that the connection at the base of the column is getting the same resistance signal as the key itself, so I know if its VATS, that the key and lock part of it is not the issue. The only problem with all this is that at no time during any of this has the SECURITY light on the dash came on or flashed. Not even during "lampcheck" (I guess that's what you call it) when you first insert and turn the key. Now, I never just paid real close attention to it before; but, I'm pretty sure that i have seen it come on in the past when you first turn the key, but I guess I need to check the bulb JIC.
At this time, let me say that both door lock buttons had just recently stopped working. My son, who drives the car, showed me where the driver's side stopped working a week or so ago. And when I was jacking with the car yesterday evening wondering if the lock switch has anything to do with it, I discovered that the passenger side isn't working either. By not working, I mean that the switches are clearly broking (the toggle is just wiggly as in no kind of springiness), and not that they are just not locking the doors. I'm not even sure that my son knows the passenger side isn't working. Matter of fact, when we went to the store together just a few days before, he unlocked my door by reaching across and pushing the passenger side button (he was driving). Is there ANY chance that these are tied in with the VATS?
I am at my wits end with this. Is there any other places that I can check curcuits, troubleshoot, etc., to at least pinpoint if it is a VATS issue or something entirely different, i.e. if VATS disables the injectors, can I look for voltage or something at the injectors or the fuse box for them to see if its out? BTW: no fuses that I've found are blown. What else mite my problem be?
AGGH! I won't my 2nd or 3rd Gen back! Waaaah!
Any and all help would be greatly appreciated.

 

Sounds like you have some aftermarket items in there. You will either have to find out what those things are or remove it all and return it to stock and then troubleshoot, if needed. All the normal troubleshooting steps go out the window when devices are added.

 

Thanks for the reply. Actually, there isn't any aftermarket on the car. Since i posted this question, I did some looking online and found out that the little box that makes the sound is the R.A.P. module. The other one that looks like it is the Express Down module. Any ideas based on these not being aftermarket items?

 

Have you checked the starter relay and socket? It is mounted behind the dash to a bracket to the right of the glove box along with the hatch release relay. It should click when you turn the key to start although it may not be very loud. I am not sure, but the hatch relay may be identical and you could swap them as a test.

 

No, I haven't tried that. But I will sure give it a try. It's by the hatch relay? Can I trace the wire from the hatch release button to its relay to help ID it?

 

It's to the far right, maybe too far from the switch to easily trace it. They seem to be identical in the service manual, not 100% sure.

If you (or someone else) don't hear it click, then the circuit is suspect.

 

here is a schematic that may help, you can see the starter enable relay (called theft deterent relay TDR in 94 and up) mentioned above. The relay is picked by the pass key decoder module (called VATS in 94 and up) http://shbox.com/1/starter_charging_93.jpg . Here is a good info source from shbox.com 4th Gen LT1 F-Body Tech-PassKey/VATS .

 

Ok, thanks a million. I will sure check it out.

 

Great info! I will study that schematic a little and see what I can trace down. I sure hope to get this figured out.

I am just the 2nd and a half owner of this car ( I say that cause I bought it from a friend who had it it since it was just a few months old). It was his wife's car, and compared to all the other early 4th gen Z28s I have looked at, and the 94 Z I owned previously, is in pretty outstanding shape for a 20yo car otherwise. Showing 131k on it now. Unfortunately, I got a hold of it about the time that some of the original components, like the water pump and AC compressor, have met there service life. Got the AC up and running, replaced the water pump ( which is an absolute PITA for me on a LT1), a few hoses and such, but now this. I sure hope it doesn't give me too much hell getting sorted out. I'm just not at a point in time that I feel like constantly tinkering on cars any more. But hey, I guess thats what it takes sometimes keeping a 20yo car on the road.

BTW, any idea if the door lock switches mite effect the VATS in any way? And, should the security light come on when the key is turned in the lamp test position? As mentioned earlier, the security light is not coming on at all. I should probably check the bulb. It might be trying to tell me something if its burned out.

 

Door locks and VATS are not related. The security lamp should light for several seconds when the key is turned on, then go out if the system is working properly. Lots of schematics on my website for troubleshooting these kinds of things.

 

Thanks for the info. I have seen a couple of pages from your site, and they are indeed very helpful. I will sure take it a look in its entirety. I am sure I will find it useful.

 

Ok, WTH? I get home this morning to start screwing with this car with all the new info that y'all have provided. The first thing I was gonna do was check to see if the "security" light bulb was burned out and if it was, if it was on to let me know that it was the VATS. So I look up under the dash and, of course, it wasn't an easy matter of just reaching up there and unplugging it without removing a bunch of dash (not what I felt like doing first off). So, next I figure I would check that relay on the right side of the glove box. I go ahead and remove the glove box altogether to better see/access it. I turn the key to the start position to see if I could hear it activating. It was mentioned that any sound it made would probably be faint, and sure enough, all I could here when I turned the ignition was that dang RAP module clicking. So, I decide to pull the airbag fuse so I didn't jack any of that up, and I reach my fingers up in there to see if I can feel it activating. I couldn't detect anything.
So now, I remember that I was gonna check the power at the injector fuses under the hood. I don't know where at for sure the VATS interrupts the injectors, but I figure that perhaps if the VATS is activated, I wouldn't have any power at the injector fuses. Well, I check with my analog meter and there is power to them. I check both sides of the fuse terminal and power is going through the fuses. So while I'm at it, I check all the fuses under the hood, on both sides of them, and every one has power (with the key turned to the ON position). Ok, so I figure I would go and check all the fuses at the left side of the dash. I move around and pull the cover back off and look at the label, and I see the 3amp CRANK fuse listed (now, of course, I have already checked and double checked that none were blown). I figure I would start with it. So, I put the tip of the positive probe under one side of the fuse, and I ground the black probe on the nut around the door light switch at the door jam. Nothing. I figure then that it may not have power unless the key is turn to the cranking position, but, I'm short one hand to be able to accomplish that. Therefore, I place the red probe under the fuse. Its not jammed in under it or anything, just the tip under it with the weight of the probe itself holding it there, and I'm not sure if it is indeed contacting the metal part to make contact. But, I reach under the column and turn the key. WTF! It makes me jump. Was that the starter! I immediately turn it again, and I'll be damn! The dang car cranks right up! My wife let out a "woohoo! you fixed it!"; but, I'm just standing there dumb-struck not knowing what, if anything, I did that might have "fixed it".
I'm sorry for posting such a long and drawn-out story; but, what gives? Did I wiggle the TDR when I was trying to feel for it activating and fix a bad connection? Did testing the power to the fuse provide some sort of temporay ground that inadvertently reset something? As I mentioned, I had already turned the key several times when checking on the relay, so what would have made this time any different? Also, I killed and restarted the car a few times without the meter in the equation anywhere and let it run for several minutes, so it seems to be OK, I guess. I hate to look a gift-horse in the mouth; but, I would like to believe it was actually fixed and not a fluke.
Any ideas?

 

There is always 12V power to the pink wire to each injector when the key is on. The ECM supplies a ground to fire the injectors. The ECM will not fire the injectors unless it receives a signal from the VATS system that the key is correct. The PASS-Key II decoder module reads the resistance of the pellet on the key, and sends a pulse width modulated signal to the ECM if it is the correct resistance. The ECM also will not permit the fuel pump (via the fuel pump relay) to turn on unless it receives the signal from the VATS system.

The "crank" fuse supplies power to the DERM (diagnostic energy reserve module) which is part of the air bag system. Basically, it turns the "AIR BAG" light on the dash on when the engine is cranking.

 

I have no real experience with this, but on another forum I was helping someone with the same problem. He said the starter relay socket had melted badly and needed replacement. Another member reported the same situation with a melted ignition switch socket. I would examine both closely. Not sure how to get to the starter relay, but perhaps removing the kick panel and/or the lower i/p panel?

 

Well, since the car "magically" decided to start yesterday, I have driven it to town, making several stops, and made it back home without incident. I guess I'll keep my fingers crossed. Now, I just gotta figure out the intermittant AC working problem. Ugh

UPDATE: ok, well scratch the previous post. Went back to town today and made two stops. My wife was driving, and when leaving the first stop while she was starting the car, she said "hey, that security lite came on". I told her it was suppose to when it goes through the bulb check, though I hadnt paid any attention if it had been coming on since it started running again, and we continue on with our second stop. Left there and came home. We stopped for a minute up at the front of the driveway at my motherinlaw's place. When we went to pull on down to the house, NOTHING. Now its back just like it was. WTF. The only thing done different than the several times before when it started working again is my wife made note that she had raised the steering wheel all the way up before she got out. Me and my son usually dont; but, I had move the steering wheel several times in the course of trying to "fix it" when it decided to start running again.
Now, from all that, can anyone make hide or hair whats going on with this damn car?