With just the vats module only (no car) is there a way to ohm anything out inside it to figure out the correct key resistance needed for it?

 

Try all 15 resistors until the module puts out 30Hz

 

How do I do that on a bench?

 

https://austinthirdgen.org/wp-content/uploads/diagram_1992_theft_deterrent_system_pass-key.jpg

https://ebay.us/m/xldgyW

Will have to mimic this schematic until to get 30hz with appropriate resistor on passkey module.

 

Im thinking that resistor in the module next to the solid state detector should be the same resistance as the key? If im correct both resistances need to be the same to take the 5 volts and reduce it to the 2.5 volts the solid state detector needs to see.

 

afaik all the f body modules were the same p/n. When new they did a learn off key resistance and then were set permanently for that passkey number. Not sure what you’re trying to accomplish but good luck

 

The PassKEY module is blank when brand new. It can be set to 1 of 15 resistance values. When it is used for the very first time it programs itself to 1 of the 15 pellet resistor values in the key. After that it is hard coded to that resistor value and can never be changed. The resistor value is programmed to a section on the chip in the PassKEY module that it "write once" only.

You are going to have to use a kit with the 15 resistor values to interrogate the PassKEY module. Start at 1 and go up to 15 in order until you find the right resistance value. You will have to wait at least 4 minutes after trying a resistor value that didn't work before trying the next resistor value.

GM VATS Bypass Resistor Kit (All 15 Resistors) | eBay

You are going to manually do what this VATS Interrogator does to find the correct resistor value for your PassKEY module then convert that resistance value to the correct PassKEY key blank number then have that blank cut for your PassKEY ignition lock cylinder.

The video attached below shows how the VATS Interrogator works. You will do the same thing just manually by hand.

PassKEY Code Designed Ohms Resistance Value Minimum Ohms Resistance Value Maximum Ohms Resistance Value
#1 0.402k (402) 0.386k (386) 0.438k (438)
#2 0.523k (523) 0.502k (502) 0.564k (564)
#3 0.681k (681) 0.650k (650) 0.728k (728)
#4 0.887k (887) 0.850k (850) 0.942k (942)
#5 1.130k (1,130) 1.085k (1,085) 1.195k (1195)
#6 1.470k (1,470) 1.411k (1,411) 1.549k (1549)
#7 1.870k (1,870) 1.795k (1,795) 1.965k (1965)
#8 2.370k (2,370) 2.275k (2,275) 2.485k (2485)
#9 3.010k (3,010) 2.890k (2,890) 3.150k (3150)
#10 3.740k (3,740) 3.590k (3,590) 3.910k (3910)
#11 4.750k (4,750) 4.560k (4,560) 4.960k (4960)
#12 6.040k (6,040) 5.798k (5,798) 6.302k (6302)
#13 7.500k (7,500) 7.200k (7,200) 7.820k (7820)
#14 9.530k (9, 530) 9.149k (9,149) 9.931k (9931)
#15 11.800k (11,800) 11.328k (11,328) 12.292k (12292)

 

https://timers.shop/GM-VATS-Bypass-M...-LT1_p_33.html

or get a tune if your keeping tpi,tbi or 3.1 or 89 2.8

 

If you don't already have the key for the car, from which you can measure the pellet resistance (not "frequency"), then you can buy one of THESE for a couple bucks, wire it into the VATS circuit and then try each of the following resistance values (not "frequencies")....



....until you hit the right one, and it starts. Airwolfe is right that it takes 4 or 5 minutes after each failed attempt.

 

Based on the many such threads posted on this site over the years concerning the PITA vats system, would it not make more sense to just eliminate it entirely?

 

A lot of people bypass it by finding the value and just installing a resistor permanently. Personally, the VATs system is the only reason I still have my car after two theft attempts, so I'm keeping mine, and keeping it in good working order.

 

I don't think that it's a PITA. I think those who say "it's a PITA", don't "get it", how it works. It's not that complicated or even unreliable in my 2-VATS experience, and does make theft pretty damn difficult.

 

If the car isn't kept in a secure garage, it would make sense to make--and keep-- the vats operational.

 

I have a spare vats module laying around, i figured it was worth a shot to see if i could open it up to figure out what resistance key it needs vs installing it in a car. i was not aware the modules were originally not programmed until a key was used. As for the car my girlfriend and I just bought to restore that is missing the keys I found a pack of resistors with each of the 15 resistances on ebay and bought those. Next is a new ignition lock cylinder with key. We want to keep the VATS to protect our investment. Thanks for the help