This is what has happened so far. I was at work with the keys to my vette in my pocket. My roommate decides to open the passengers door to the vette. The drivers door was locked. The alarm goes off for 10 minutes and then she said it stopped. The car will not crank The security light blinking. Ive put my keys in both of the doors turned them 90 degrees still no crank, ive put the keys in ignition turned to run and lock, no crank, changed starter no power going to purple wire on starter. so i bought starter relay did not work. my car is a straight drive changed clutch switch on pedal still no start. now ive puchased the lock cylinder bypass #3 measured my resistance it is 679Ohms that did not work either. Is there a reset button some where the car acts like Im trying to steal it. But i guess i dont know how to disarm it! Ive unhooked the battery and checked both the vats fuses they are good.Please any suggestions . Thanks Leslie

 

First, jump the clutch safety switch and try a crank while you measure the voltage on the jumper. The jumper should have 12v during crank position of the ign sw. If not, then the start enable relay is not closed. If it does have 12v, then starter motor is defective. Next, bypass VATS. Remove the hush panel above drivers feet and find the two wires coming out behind the steering column that go to a 2 pin connector and unplug the connector. Clip a 680 ohm 5% 1/4 w (or larger power) resistor across the 2 wires going into the wiring harness (these go to the VATS module). Radio Shack sells these resistors and will work fine. If you still don't get a crank and no 12v across the clutch safety sw during crank, then you have a defective start enable relay and it should be replaced, but first observe if the relay closes in crank position. Either the relay coil or its contacts are defective or the VATS module is defective. Insert your key in the ign sw and measure the resistance across the 2 wires from the steering column. They must measure the same as the pellet (680 ohms) or your contacts that make with the pellet are worn out and the ign tumbler needs to be replaced. Don't permanently bypass VATS because 99% of thefts are done by bashing the column and jumping the ign. About 6 years ago my 87 I drive every day left me stranded at church. I bypassed VATS with a resistor and had the ign tumbler replaced and have had no problems since.

 

Please explain how one resistor fits all for the vats module. JFB said a 680 ohm fits all? I thought there were 15 or so different key/resistor combinations and it had to be the correct value to get past the module. I'm new to the whole vats thing and would appreciate any input. Thanks.

 

I would suggest disconnecting the (-) battery terminal for about 30 minutes. While unhooked and your waiting, check the battery voltage with a volt meter. The battery may just be dead from the alarm going off for so long. Hence the no crank. If the voltage checks out, then after the lapsed time, reconnect the battery. Should work at that point.

Make sure you check the voltage of the battery though.

 

Reading is fundemental!!!!!!!!!!!!!!!!!!!! Leslie Smith posted that his pellet measured 679 ohms. Show me where I said 680 ohms works ALL VATS modules !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!

 

Horn alarm activation is not directly associated with the Vehicle Anti Theft System (VATS). The Universal Theft Deterent System (UTDS)sets off the horn alarm, and LIKE the VATS, will not allow a ground for the start enable relay, thus no crank. For model years 90 and later, the Central Control Module and associated sensors is responsible for both VATS functions and the UTDS. I do not know if the MY 88 has a UTDS module. If it does, I'd be looking at the door disarm input signal or a fualty module.

Keep in mind, I do not have a service manual for your car. I suspect there are some common features and components associated with both earlier and later(MY(90) versions. The door lock system provides a "disarm input" when a key is used to unlock the door. If the UTD alarm system has been armed and the door is opened without the disarm signal being recognized by the UTD, then the alarm will sound and no ground for the start enable relay. If your UTD system is active and the door lock disarm signal is not working, no start. If the door lock signal is good and you have a bad UTD module, then you still have a no start.

As a general view, when a no start condition is initiated by honking horns, I head for the UTDS trouble shooting chart. Otherwise, I hook up the scanner and determine if a code 46 is present and other serial line data from the ECM.

In summary, if the horn starts honking upon vehicle entry, it has NOTHING to do with key pellet resistance. I'd look at the UTDS.

Let us know. Alway curious.

dlmeyers 90 coupe zf6 3speed shocks

 

One other suggestion. Check the owners manaul on how to disarm the UTDS. On my car, you use the key to lock the doors. Not sure on how yours works. I'd think disconnecting the battery should work.

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Ive been outside and disconnected the battery for thirty minutes. Still no crank. Checked volts on Clutch safety switch. No volts when jumped. I checked volts at starter relay there are 11 1/2 . I checked ohms on ignition wire they are 679 with key in ignitioion and 679 with key turned to start. i dont have a resistor to jump vats system yet. Ill get one tomorrow. what do you think ????

 

If you measure 679 ohms across the wires from the column with the key inserted, then you have good contacts in the ign tumbler. If you see no voltage on the clutch safety sw jumper when the key is in the crank position and 12v on the start enable relay, then the wire (gn/wht on my 87) from the start enable relay contact that goes to the clutch safety switch is open and you need to find where. Make sure that there is 12v on the wire from the ign sw to the start enable relay coil and movable contact arm (yellow on my 87) when the ign sw is in crank position. If not, then ign sw is defective or the yellow wire is open. Make sure that the VATS module grounds the other start enable relay coil wire (green on my 87) grounds when ign sw is in crank position. If not, you have a defective VATS module or open green wire.
Also, you can jump the green wire to ground and see if it will crank, but if the VATS module is defective, the injectors will not pulse and the engine will crank but not start.

 

Here's some info on the subject
http://members.shaw.ca/agent86/Vats%20Electrical.pdf

 

If it ain't broke, don't fix it.
I agree with what dlmeyers posted. I think the alarm system still thinks someone is try to break into the car.
Agent 86 posted the Forced Entry Alarm System for the 86 and it looks the same as my '87 setup. If you read the section for System Check you will see that in order to "Arm", "Disarm" or "Reset" the alarm system, they are very specific about which door to open or close. They are specific as to which door lock they want locked or unlocked. You locked the left, your friend opened the right. The Security Light is wired through the Forced Entry System, not the VATS.
I think it just needs rebooted. I want to rule out that your lady friend broke your car by just opening the door. I suspect that the '88 is wired a little different and so you need the book or for someone to post those pages here. It may have a different procedure for arming and disarming the system.

 

Take a look at page 7 of that PDF. My Starter enable relay went bad.

On your manual transmission the path goes from the key to the starter enable relay ON yellow wires (which is behind the center info center - where the idiot lights are) to the clutch switch on a dk green/white wire. If you checked the voltage between the clutch switch and ground and did not see voltage - that means that the starter enable relay is not closing.

That could mean one of two things - the relay is bad OR the computer is telling it not to.

 

Don't forget that the pdf is for the '86. dlmeyers said that on the '90 the the VATS and the Forced Entry System are connected.
Look on the first page of the pdf on pins "E" and "L" of the Theft Deterrent Controller Module. It looks like it had the capability to control the VATS, even in '86. It just wasn't connected.
The VATS will shut down for four minutes if you try to start it without the right key. During that four minutes, it won't start even with the right key and each attempt will restart the four minute timer.
I think the Theft Deterrent thinks someone is breaking in and is telling the VATS. One look at the '88 pages would tell if I'm blowing smoke.

 

My bad JFB. I need to get hooked on phonics and pay attention or something.

 

Hello Leslie and all,

The 86 schematic was very informative. Thanks for that Agent 86. If someone has the 88 manual(s), could they head to around page 8A-133-0 and see if the "Theft Deterrent Controller"(TDC) has wires labeled starter interupt control or any wires heading to the start enable relay. Need to determine if the 88 TDC influences the start enable relay after signals from the Forced Entry Alarm System. After reviewing the 86 diagrams, it's clear this system has evolved over the years. Don't know when this module interfaced with the start enable relay. It may have been in 89. Just not sure.

Page 133-5 comments on how to deactivate the alarm system with the door key for the 86. This is similar to my 90's owner manaul instrtuctions.

The schematic for the 88 would help determine how this system is structured for your model year.

I've ordered a set of diagrams off ebay but don't know their quality. Will keep you informed.

Oh, I should mention I am somewhat familiar with this system. While in a parking lot at a packed exhibit, I opened the driver door, used the auto door lock to secure the doors(not a good idea), moved to assist a passenger. Since the passenger door was CLOSED and locked, passenger attempted to open the door from the inside, and off goes the alarm. The system believed someone had broken the glass, and reached inside opening the door, an intrusion. At any rate, I hustled around to the other side and used the door key to deactivate the alarm. I'm sure some Ford guy was thinking idiot Corvette owner. Not far from the truth.


dlmeyers 90 coupe zf6 3speed shocks

 

I would not entirely rule out the starter, unless I may have missed something in the postings.

I once worked on my car to fix an unrelated issue to starting. Got it all buttoned back up and went to start the car. NOTHING> Rechecked everything I did, and still nothing. Couldn't figure out what it was.

Pushed the car back into the lift, got it up where I could check the starter. Verified that I had 12v to the starter. Had my father up in the car on the lift, he hit the key, and 12volts came to the solinoid - the started however did not kick on. Went to the tool box - got a hammer, gave it a good rap, and then it kicked on and tried to start. Took it out and got a replacement and all was well.

It really was a baffling moment and I spent about 3 extra hours checking everything I did, until we deemed it had to be the starter. Sure enough it was - sometimes one event causes us to stay off the real problem. In my case, or maybe even yours, I would have been onto the starter instantly after checking the battery voltage. But I wasted hours checking what I had already done - thinking it was the problem.

Something to think about.

Have you checked the voltage down to the starter? When some hits the key. If the solenoid is getting 12v, then it has nothing to do with the VATS. I would try checking that if you haven't already.

 

[QUOTE=ski_dwn_it]I would not entirely rule out the starter, unless I may have missed something in the postings.

Haven't ruled out a coincidence either. Hard to give advice without knowing how the system is wired.

Darn cars.

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On page 8A-133-0 of my 88 FSM it shows Pin E as Starter Interupt Control (not used) on the TDC. In the schematic on page 8A-133-8, it shows only 3 units with input to the Starter Enable Relay, the ignition switch, the VATS decoder module, and the transmission position switch or clutch start switch, depending on tranny.

 

I had somewhat the same problem with my 87 last Spring. I used my Helms and followed the diagnostic flow sheet. When I got to the point where I bypassed the VATS control module it started!
I just sold the car yesterday and gave the new owner my Helms so I cannot help you out by looking at it. If you do need the control module I got mine from www.vette2vette.com for $100 (GM dealer quoted $300). He had all of his tested by Gordon Killebrew and then wrote the correct resistance on each one. Here is a pic of where it sits behind the breadbox. It is the grey square object in the middle. Note: you have to remove the upper dash pad and the breadbox to get to it.
Good luck!