87 WITH VATS. What is the easiest way to disable it?

 

MAD has a plug and play.

 

This may help.


VAT key codes and values -- 1 of 1
Date Published: 2002-04-14

Submitter's Name: Gary Spencer
Email Address: Private
Corvetteforum.com Member Alias: Blue 92

Someone posted this a while back in C4 tech. Corvette VATS Key Codes and Associated resistance Codes in OHMS Pellet Resistance Code Ohms 1 - 402 2 - 523 3 - 681 4 - 887 5 - 1130 6 - 1470 7 - 1870 8 - 2370 9 - 3010 10 - 3740 11 - 4570 12 - 6040 13 - 7500 14 - 9530 15 - 11800 VATS, these four letters can instill fear in even the most stalwart of Corvetters. The Vehicle Anti-Theft System was introduced to the Corvette for Model Year 1986 and has been a thorn in the side of many 1986 - 1988 Corvette owner. At this point a discussion of the system is in order as there are many misconceptions concerning this system. VATS SYSTEM The key (pardon the pun) to the system is the special ignition key that contains the resistor pellet, this pellet connects to the VATS module which allows it to: 1. Signal the ECM. 2. Close the starter circuit. Without a signal response from the VATS module, the ECM will not allow fuel injection or starter operation. VATS is not connected to the alarm system, so it is active even if the alarm system is defeated, or if the car is left unlocked. The two main components of the system are the ignition key with resistor pellet and the VATS decoder module. The pellet in the key is just a resistor, it will be one of 15 specific values. The ignition cylinder has contacts that connect between the two sides of the ignition key pellet. Wiring carries this resistance value to the VATS decoder module, where it is compared to the value stored in the module. If they match, the car starts. If they do not match, the starter circuit and fuel injectors are disabled. A timer (approximately 4 minutes) is also activated if an improper resistance is read. Each time an attempt is made during this delay period, the timer will be reset. So it is important to wait at least 4 minutes before another attempt is made. The main problem with the system in the first three years of production was the material that the contacts of both the ignition key and ignition cylinder were made of. This material was prone to premature wear, causing poor contact, an incorrect resistance being seen by the decoder module and a no start condition. This caused embarrassment when your shiny Corvette wouldn't start and your significant other laughs uncontrollably and offers to drive you in her Civic. It also causes inconvenience and more embarrassment when you need to call the AAA for a tow. Band-aides were developed that would fool the decoder module. These Band-aides bypassed the key pellet and the ignition cylinder contacts. The VATS Bypass Modules that you see in the Corvette catalogs cost anywhere from $30 - $50. Add to that shipping and sales tax where applicable and you’re looking at $35 for a resistor that you can pick up at Radio Shack for under $1! Another problem with the bypass modules is that you have to know what code value (1-15) to buy. That means you'll have to go to a dealer that can use their VATS Interrogator. If you take a multi-meter and measure the resistance between the metal contacts on either side of your key, you can buy a resistor of this value at any Radio Shack store. ¼ watt will do. You then need to remove the hush panel under the steering column. Disconnect C281 (two-cavity connector at base of steering column with two black wires in the female end and one yellow and one brown wire in the male end). Your newly purchased resistor goes into the male side of this connector, so you'll need to crimp a couple of female pins to the resistor legs. If you insist on purchasing the VATS bypass from one of the Corvette catalogs, again measure the resistance of your key pellet and compare it to the code chart to find your code. It is also possible to reprogram the PROM to ignore the VATS signal, but that is beyond the scope of this article. The real fix came from GM in July of 1988 as TECHNICAL SERVICE BULLETIN number 88-292. This TSB includes the part number for a new ignition cylinder that has better contacts. Keys have also been updated that are slightly longer and have the better contacts. This virtually eliminates VATS problems caused by connections. You still want to keep your key clean and dry, but with the TSB competed, you should enjoy VATS problem free starting for a good long time.

 

99% of thefts are done by bashing the column and jumping the ignition. If you bypass VATS you are a candidate for donating your Corvette to some scumbag !!!!!!!! If you are having trouble with VATS preventing a start, it would pay to find out where the problem is instead of bypassing VATS. First check your clutch safety switch by jumping it (gear selector switch if auto) when you cannot start. Then remove the hush panel above the drivers feet and find the two white wires from behind the steering column that go to a 2 pin connector and unplug the connector. With your key in the ign, measure the resistance across the white wires. It should be the same as your pellet. If over 13k ohms, you need a new ignition tumbler which has better contacts that make with the pellet. You can temporarily bypass VATS until you can get the new tumbler installed by connecting a 1/4 watt 5% resistor the same value as your pellet and from Radio Shack ,across the two wires that go into the wiring harness (VATS module).

 

I appreciate the excellent advise you all have given.
Now at least I know where to start!
Reguards
John

 

VATS saved mine once many years ago.

 

Umm I got rid of my vats, and never looked back. The whole "Oh, look.. it won't start and I have mid terms in 30 minutes" thing got old

Anyway, go measure your key pellet with an OHM meter. Mine was 680. Go to radio shack, and buy the closes resistor they got to that impedance. They happaned to have 680 as a choice, so that was easy. You get like 6 resistors for a buck. Don't worry about wattage, since even the wussiest 1/4 watt should be overkill for the tiny leads.

Drop down your driver side hush panel, and start looking under the steering column for two super skinny wires. They'll be much smaller guage then any of the others, and mine were brown and yellow. There will be a connector on these two wires. Disconnect it. Ignore the end that's going up to the key cylinder. Let that dangle, or tuck it away - doesn't matter. The side that goes back into the dash however, is important. Use your favorite method of reliably hooking up electric stuff together (I used solder and brush-on insulator) and connect the two wires together using your handy resistor. If all is right, your car should start at this point, and the ECU will always think the pellet is in the key cylinder.

Notice that this only kills VATS, and you will still have the alarm function when you lock your car up

PS. Solder really was overkill, I just wanted it done 'right' - when I was first testing it, just inserting each leg of the resistor into the plug was fine

 

i disabled my vats exactly like the post above. after i dialed in the right ohm on the variable resistor the car started then i super glued the top of the resistor so the dial couldnt be moved. the only reason i did this is cause all the mods iv done during the process i got stumped for about a day on a mod i had installed the car wouldnt start as it turned out it was the vats. as stupid as i was the vats was removed from futher trouble shooting. now i have a kill switch. wanna know where it is?

 

hoot85, if you find that you need a new ignition lock you will need to pull the steering wheel to remove it. In that case let me know and I am just a little north in Rockland Co and am willing to drop off the two tools to remove the wheel & lock plate.