I have been haveing an intermittant no start problem and today it finally stayed failed so that I could make a couple of checks. There is no power to the clutch safety switch. I will have time tomorrow to pull the dash apart and get to the starter enable relay and check the situation with that. Assuming that there is power to the relay and none coming out, I intend to bypass the whole Vats system and I am contemplating either jumping the two terminals that feed power to the clutch switch or just grounding the coil output which is what the Vats module does. Has anyone ever done this?

 

Mid America Designs sells a VATS Bypass Module for $24.99. I would think that it would amount to more than shorting 2 wires together, but you never know-Good Luck

 

Bypassing VATS permanently is a very bad idea. VATS keeps thieves from stealing your car by bashing the column and jumping the ignition which is how 99% of cars are stolen. The person I bought my 87 from came out of work and found her 90 vette with a broken drivers window and bashed column, but the car hadn't moved an inch.
You can determine if your ign tumbler contacts aren't contacting your pellet by finding the 2 wires from it that go to a 2 pin connector to the VATS module. On my 87 they come out the bottom of the steering column and go under the carpet. Unplug the connector, insert your key and measure the resistance across the wires from the tumbler. It should measure the same as the pellet. If over 13k ohms, you need a new tumbler installed. You can temporarily bypass VATS by connecting a fixed resistor the same value as your pellet (5% resistor from Radio Shack will do it) across the wires that go to the passenger side (VATS module). Of course the start enable relay could also be bad, but the resistor is a cheap trial.

 

I appreciate what you are saying about the effectiveness of the VATS system, but I don't really leave the car anywhere and being an 86, I think it has lost its real theft appeal. While I am sure it is still possible for someone to steal it, I am more concerned with it stranding me like it is doing now.

Anyway, my plan to bypass the starter enable relay won't work because VATS also disables the fuel pump. So next step for me is to determine whether it is the relay or VATS that is interrupting the power, later today or this weekend, I will see what has power at the relay and go from there. Thanks for the tips on checking the tumbler contacts.

 

VATS also informs the ECM to not pulse the injectors if the correct pellet resistance is not present. And......86 vettes are stolen every day!
When your left headlight burns out are you going to epoxy a flashlight on the left side of the hood? Just install a new tumbler!


[Modified by jfb, 9:52 AM 5/21/2004]

 

First, you can't jumper the two terminals that feed power to the clutch switch to bypass the VATS. The A terminal of the Clutch Switch goes to the Start Enable Relay, so if it doesn't energize, you'll have nothing at the Clutch Switch. Grounding the Start Enable Relay would allow you to crank, but that is only half the VATS battle. The other side is the VATS output to the ECM for cranking fuel enable. With your Start Enable Relay coil grounded at the Dark Green wire, but without the cranking fuel enable to the ECM on the Purple wire at B6 of the ECM, you'll crank, but the engine won't fire. The way around this is to use a squarewave generator at the VATS Module pin P (purple wire). Gordon Killebrew sells one of these or you could have a new PROM burned that ignores the VATS input and always enables fuel. The choice on bypassing the fuel signal is yours, but you will have to do both to completely eliminate the VATS. The bypass kits sold by the Corvette houses are only the resistors that jfb described in a nice easy to plug in housing. All it does is tell the VATS Module that the key resistance is always correct. This fixes the majority of VATS problems as it takes the key and Ignition Cylinder contacts out of the loop, but does nothing for a VATS module failure. Your idea of a bypass would be a true VATS bypass. I also agree with jfb in that it is much better to correct the problem and keep the added protection than to permanently bypass. I have a bypass box that I made that replaces the VATS Module behind the breadloaf with a box that has the L pin (Black wire) connected to the V pin (Dark Green wire) to ground the Start Enable Relay and the squarewave generator's output on pin P (Purple wire). I do this for temporary situations when the problem is in the VATS Module itself (rare). I have another little box with a 15 position switch (for the 15 different key resistances) that plugs into the Igntion Cylinder Connecter under the driver's side hush panel for most temporary VATS bypasses. Again, I wouldn't do this permanently, but a single resistor or a few resistors connected together to equal you key's value (as described by jfb) as a temporary measure until you can get a new Clyinder or the time to do the job, will keep you going in most instances.

Good Luck.

 

If the VATS hasn't been disabled, how is this possible :confused:

Sky, I bypassed mine, and it can be done for a couple bucks. I can give you very specific instructions if you require them.

 

lost keys to my 87 corvette how to bypass vats completely please help thanks

 

This is an opportunity to get a new chip burned with vats bypassed and fan control temps changed.

 

You need to start a new thread since this one is 9 years old.

Since you asked though, I'll point out several problems you have as I went through the same thing years back in my 91. Since you no longer have an ignition key, you obviously can't turn the lock cylinder. GM's records that far back are spotty at best, so its unlikely your ignition key cut will be on file (it wasn't for my 91). This can be remedied with a new ignition cylinder. The car still won't start due to VATS. However, you can't bypass VATS without having the proper resistance from your key (15 possibilities). I installed a new ignition lock cylinder and duplicated each of the VATS resistances using a potentiometer until the car fired up. It was a long, pain in the azz, process, but it worked. In retrospect, I'd call a locksmith and see if he can help you. I've heard some locksmiths have a tool called a VATS interrogator which might help you.


Here's my thread


http://forums.corvetteforum.com/c4-g...s-for-car.html

 

Here...

This is the fastest, cheapest and easiest way to do it RIGHT>...

simply remove the VATS module buried in the passenger side dash under the lower panel.

Wire in the bypass module as instructed. 2 or 3 wires. Solder or crimp...make it secure.

DRIVE worry free.

all for $15 <-------- seriously ! $15.

It works, everytime and I can prove it....MY car starts everytime.

http://www.ebay.com/itm/GM-VATS-or-PASSkey-II-Bypass-Module-For-LS1-and-LT1-/281064956739?pt=Motors_Car_Truck_Parts_Accessories&hash=item4170c6e343
This module is designed to work with either early VATS or LT and later passkey. It has different wires to use depending on your yr model. Very easy to install. Finding the VATS module in the dash is wayyyyyyyyyy more difficult than installing the bypass !

You can also buy a new module. $100 If you want to keep the system. I keep the bypass installed BUT do have the new module to plug in if I go somewhere that may be shady....

Good luck !

 

That module only supplies the fuel enable signal required by the ECM to pulse the injectors ;
you still have to manually bypass the starter enable relay also controlled by VATS

 

Thanks for that info but they are a few vette men on here that said (very bad idea so for now im going with key bypass i have tryed 9 resistor no crank now i cant get my fluke 87 true rms multimeter to add over 3.0010 thanks for any help

 

Key bypass is not a VATS bypass. Its a KEY bypass. The car is still shut down by VATS.

Whats a bad idea? I do NOT like driving around without VATS, that is why mine works now when I plug in the new module. I run off bypass locally. Any road trips...unfamliar places gets the module plugged in.

 

maybe...I am not sure. I have my starter enable on a toggle so I can cut that

 

What do you think the key bypass is going to do then?
It fools the VATS module into thinking the correct key is in the Ign all the time so VATS is permanently bypassed

No it is not ;
so long as the correct resistor is in place VATS is bypassed ( which is the whole point of doing the bypass in the 1st place )

The fact you previously failed to mention that your bypass device is removable make a lot of difference to it's operation.
Most install the bypass as a permanent feature

Once again , you forgot to state that little fact that makes your install different to what most do
All you stated above was you installed the fuel enable signal generator off eBay

 

why cant i unhook the two wires comin from the key switch take my multimeter get the resistence from the two wires then make me a resistor of the same vaule will that work for my 87 vette 3 time trophy show car winner with lost keys?

 

[QUOTE=vetteoz;1583494890]
What do you think the key bypass is going to do then?
It fools the VATS module into thinking the correct key is in the Ign all the time so VATS is permanently bypassed


No it is not ;
so long as the correct resistor is in place VATS is bypassed ( which is the whole point of doing the bypass in the 1st place )


ok, I may be mistaken and if so, I would love to have the facts,..

so you have your resistor 'kit' installed. Now the key switch is a closed circuit...good to go, nothing to go wrong THERE.
But, does not VATS get involved if there is a forced entry? and then initiate the same no crank, no start features as if there were a screwdriver jammed into the ign switch?
If this is true( makes sense to disrupt the starter & inj system if the alarm side were tripped) then the key bypass has only "bypassed" the key switch ?-->and VATS can still shut it down via forced entry module?

Going to the books. I have to be fair and admit that I assumed F.E. was also able to engage a VATS shut down... I may be way off base, but to me that would make perfect sense to shut the starter and fuel down IF the door were violated.

 

A little background reading for you
http://www.thirdgen.org/vats_passkey_system

VATS only disables the engine if it does not see the correct key ( or equiv bypass resistor ) being used when the engine is cranked over ;
has nothing to do with the door switches that activate the horns on forced entry
Check out the circuit diagram in the link above ; no connection to anything related to the doors

 

Ok...
guess I get to leran sumthin today..

I see in the drawing where the TDM has its pins for starter enable and a blank next door, so that tells me that it was possible to join the 2 systems so they could act as one but never did as far as I can see. Wonder why? Seems like a violation of the doors or hood should secure the vehicle by making it a noisey PITA, AND unable to start up, but they didn't. So I'm back peddling on this. The 2 should go together, to me anyway. Break in and the car should self secure by locking the starter out and the injectors. But this one just makes noise. Now I understand why people thought they had to run out and buy another alarm system...the 2 from the factory were not linked..making them usless to
each other. That just does not make sense..
It is what it is though..