kroqz28gto

Here's the problem with my 1996 Z28.. This has happened several times and is driving me nuts. I put in the key, turn the key to the first click and everything works normally, when I turn the key to "start" I get a complete electrical failure. Nothing works. It's as if someone cut the battery cable. EXCEPT the security LED flashes, and I get the normal key in the ignition ping. But say I hit the light switch at this time, then I lose everything, even the LED and ping noise. If I turn off the light switch, the security LED starts flashing again. It's a complete meltdown. The car gets no power to anything! When this happened last night I disconnected the battery cable and a 1/2 hour later, hooked up the cable, and bingo, everything is back to normal. Car runs fine. Now, this has happened about three times. Would a body control module failure cause a complete wipeout of everything? I looked at the service manual, and it seems that an anti-theft system failure would not cause a complete meltdown. So, would a starter solenoid failure cause a complete meltdown? Alternator failure? I suppose loss of ground to battery would cause this, but what is strange, is the LED light flashes. So, it is getting power to there. I don't think the entire car's electrical system goes through the body control module. I know there is BCM relay, but again, a complete meltdown if this fails? Anyone have any ideas? I'm afraid to take this car anywhere until I figure this out. This morning I start it and everything is fine, the remotes also are fine, they work properly.

HBHRacing

The security light flashing when the key is in the on position indicates a fault in the Pass-key system. The first thing that I would test would be the key cylinder.

Use an ohm meter on the key. One probe on the one side of teh pellet and the other probe on the other side being carefull not to touch the leads with your fingers. Then unplug the 2 wire connector at the botom of the colum (2 white wires in an orange sheeth) now stick the key in the tumbler and turn to the on position. stick your meter probs in the connector thats going up the the colum. if you get the same value your fine and it's something else. if your geting an open on "infinite" value then you have a broken wire at the tumbler and it needs to be replaced

BlownF1

Yup, sounds like the VATS...do a search on that and you'll find tons of info. Sometimes you can use your spare key for a little while longer, since the resistor pellet probably isn't as worn on it. In the end though, you either need to decide to replace the ignition cylinder, or bypass the VATS.

VegasZ

Heres a little trick to avoid problems with VATS. When you put the key in, wait a half second before turning. This way the computer has time to read the key. The security light has never come on on me after I started doing this.

kroqz28gto

I want to make sure I understand this. With an Ohmmeter, I measure the resistance, putting the leads on either side of the pellet in the key. Then, I put the key in the ignition, disconnect the security wire (yes, the orange/white wire--very small awg), then turn the key to "ON" ---which is the position just before "START" and measure the resistance. The resistance in the pellet and the resistance in the wires at "START" should be the same, right? Since this is an Intermittent, the time to test this would be when there is a failure. Which means I have to drive this car until it fails with an ohmmeter in the trunk.
I suspect you are right. What I don't get, is why there is a total, complete meltdown. You would think the lights would work, the 4-way flashers, something.

HBHRacing

yes. the resistence value with the key in run shoud match the keys value. when you turn to run the signal goe sto the decoder module and if it matches the stored value will alow the theft module to send teh start signal and alow for fuel enable. if you ever unhook the starter selinoid wire and crank the car all the lights will go off when your in teh crank position. just like when you have teh radio and air on wwith the kry in on and go to start teh car they shut off for a sec. your just used to teh car starting and them coming right back on

BlownF1

It's been awhile since I had to deal with it, but I don't think VATS kills everything as you're describing...perhaps you've got a short then. It'll keep the car from cranking, but that should be about it. Anyway, the time to check the ignition is anytime, it doesn't have to fail to test it. In the ignition cylinder is two contacts that wear over time, you can take a flashlight and look inside where you put the key to see if they look worn/spread apart. When they fail to make good contact, and you turn the key, that's when it "fails" because it thinks someone is trying to steal the car without the properly coded key.

kroqz28gto

Absolutely correct, I never thought of that. Everything does lose power except the starter. Bingo. Thank you for your help. This Web site is really a lifesaver.
As far as testing, i would think the time to do it may be when it fails? Because when it's running properly, the resistance should be correct otherwise it wouldn't run? In the service manual it does mention that the key can be taken to GM for testing. I'll do that today. I only have one key, but I did have that column apart about a year ago because one of the "pivots" on the tilt came apart and the column had a lot of slop in it. When I put it together the orange/white wire was accidently cut and I spliced it, then taped it. Looks like that column is coming apart again...
I have another technical question. This car had a bad head gasket and I replaced both. There is a code coming up that the driver's side converter is "low efficiency." Makes sense, the anti-freeze destroyed the converter.
Now, I've been ignoring this because it seems to me that all this is doing is putting a little more pollution in the atmosphere. But i wonder. The car seems to bog---hestitate on pullout. I've checked the plugs and the rims have a bit of carbon on them. Do you think that the O2 sensor behind the bad cat is somehow affecting the fuel curve on the car? The exhaust doesn't smell rich, the gas mileage is about 17 in the city, over 20 on the highway. The distributor cap, rotor, plug wires, plugs, coil are all new GM parts within the past 3,000 miles. There is no fault code for any O2 sensor on the car.

HBHRacing

first off how did you "splice" the wires together? anything other then direct wire to wire conatct runs the risk of changing the resistence value and there by giving you some issues.

when GM "tests" the key they just do the same thing that you do with an ohm meter and crosing it with there chart to make sure that it falls in range of the correct value

kroqz28gto

Well, the wire was pinched when I put the column back together. The car wouldn't run. After taking it all apart again I discovered the problem. I just cut the wire, twisted the ends together and used black electrical tape over everything. Bad idea, huh? It's been fine for about a year and a half, 10,000 miles. But in the last month these problems have started. I took the key to GM today, the parts guy said it's a number 10. I looked in my parts disc and apparently there are 15 different codes.

HBHRacing

I;ll bet one of 2 things.. either the wires faling off and making intermitent contact or it;s grouning itself out. time for a key cylender.


yes tehre are 15 different values. a number "10" should ahve a nominal value of 3740 ohms and a high/low range of 3590-3910. Thats where the value will work.

kroqz28gto

This is exactly my thought. Thank you for your help. Will post when I get this corrected.