Decided to check mine today. Set the ohm meter and got 2.99 on all 3 keys. Now is there a 2.99 or should that be rounded up to 3?

 

I found this:

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.




[Modified by Blue 92, 12:00 AM 1/10/2002]

 

Then what am I doing wrong. I put my meter on ohms and place a contact on either side of the key. I got 2.99. That's not in your list. Now I'm really confused?

 

3 ohms isn't right. That's way too little resistance for the key. What you're doing wrong IS!!! .... you need to check the resistance of the little tiny piece of metal that is encased in plastic on the key.. not the key itself. The key should be close to 0 ohms since it is a solid piece of metal... which is what you measured..

 

I did it that way. On all 3 keys, and got the same 2.99???? :confused:

 

Uhh.. hhhmmm... perhapse 2.99 is 2.99kOhms .. not 2.99Ohms. Check the setting on your multimeter and be sure that you aren't reading in kO .... :D

 

Since my meter only reads in K ohms now that I look at it :eek: , I think we've found the answer. Thanks. :cheers:

 

I found TSB 882928A listed at ALLDATA and The Viper Pit, but couldn't get the actual bulletin to read. I'd like to get the updated cylinder & key...Does anyone have a link to the actual bulletin???

 

Ummm...thats off by just a little. The No 15 is actually 11800 Ohms. :smash:


:lol: :lol: :lol:

 

Blue 92,
Can I ask where you got that?

R94 LT 1,
I suspect you have a code 9.

Rich B.,
I've got it at my site where the bit that Blue 92 quoted originated. Go direct to it here http://www.corvetteforum.net/c4/rayq...sbs/88-292.htm


[Modified by Ray Quayle, 1:13 PM 1/12/2002]

 

That's what I'm thinking, but Glock'94 ran a computer scan the other day and now we're not even sure if the VATS is turned on! :eek:

 

Thanks, Ray! I like to have that part # handy... :D

Does anyone know how close the resistor has to be to the code??? Fr'instance, if I have a code 7, can I use a jumper resistor of 1820 ohms?...

 

Resistor values are pretty standardized, so a 1820 ohm resistor will be next to impossible to find.

What you be able do is find a 1.8K ohm 1% tolerance resistor, and put it in series with a 50 ohm 1% tolerance resistor. This will make close enough to the same total resistance to work.

The good thing in this case is that since your value is going to be slightly under the specified...it should not have any problem down the road, since resistors typically increase resistance with age.

 

OK; sounds right. I had found the 1.82k 1/4 watt 1% resistor in the Radio Shack catalog...But I already know how far to trust Rat Shack...

So a 1.8k and another near as possible to 70k (RatShack shows a 68) in series should do it...Or maybe the 1.82k and a 51 will do it...

I suppose I better take my multimeter with me... :D

(Luckily resistors are cheap!)...

 

Shucks, Blue, this post of yours needs to be in C4 Tech Tips. I've been looking for the key values for two years now. Thanks!

 

...And a big "Thank You!" to Ray Quayle for posting the info on his site!... :yesnod:

...(As well as "Thanks!" to Blue 92 for directing attention to it)...

 

Hey, lets get a little credit going this way! :jester I'm the one that posted the topic! I didn't think it was that technical till I got the answer! :cheers:

 

...You couldn't even read the ohmmeter!!!... :D

...But OK; here's my blond 16 year old daughter; she's pushing her lips against the monitor...Go ahead; kiss her back...And Thank You, Sir! for starting this educational thread!!!... :cheers:

 

:lol: :lol:

 

Ray,
It was posted here a while back and I thought it was worth saving. No idea who it was but I can't claim any credit for it. :D

Are you going to be at CFIII? We'll be having another great time at the Baymont.

:yesnod: