ken3983

Picked this up off another site. I want to build it and try it whenever I got off from work. If someone else builds it, try it and post it here on Thirdgen. Pretty simple and readily available parts.

When the vehicle's EPROM cannot be reprogrammed to "turn off" passkey, the vehicle's Passkey module or a clone must be used. An ECM programmed with the Passkey option requires a 30 or 50 hz 50% duty cycle square wave in order to enable the fuel injector outputs. The signal is only needed during cranking to get the engine started. This simple circuit can be built for a few dollars using parts that are available at Radio Shack. Below is a picture of the circuit built on a small PC board, and the same circuit being tested with a scope. For PASS-Key systems (30hz) R2 should be 22-23k ohms. For PASS-KeyII systems (50hz) R2 should be 13-14k ohms.


Ken

Dale

iTrader: (12)

passkey and vats are two different things.

You can bypass vats on these cars(not passkey) for about 25cents and alot easier then making that. All you have to do is know the resistance your key/box is set for.

cooltc2004

iTrader: (4)

I was wondering why you guys disable VATs?

Stealthy-One

the key an ignition gets old adn dosent have as good a contact any more so the ECU thinks it has a different resistance pellet in the key.

ringo234

Dale

iTrader: (12)

Like said, key goes bad. But half the time mine has acted up I just blew into the key hole, it worked. Or I warmed the key up, as well cleaned the key.

Or, something else in the system acts up. The vats ecm(different from the engine ecm I belive), or a relay, the switch, etc.

Six_Shooter

iTrader: (2)

Sometimes VATS is refere3d toas "Passkey", thePasskeythat you are thinkin of that is different than VATS i "PassKey 3", whihc is anewer sysem that is transponder based.

The "25 cent" fixi s only good i the VATS module is still good AND you know the resistance that is needed.

The above posted system is for connecting directly to the PCM, getting rid of the VATS module completly. Usually used for swaps where the VATS module was not included with the PCM.

Dale

iTrader: (12)

I know, I used one on my SFI swap in my s10. I thought the gen4 system is different then the ours though?

Six_Shooter

iTrader: (2)

While the protocol in the VATS module may differ a bit, the basisc needs are the same.

MrDude_1

key goes bad..... then just get another key cut.
problem solved.

ken3983

I'm kinda agreeing with SixShooter. I went out the other morning to go to work and turned the key....nada. I knew I has bypassed the system with the resistor a few months ago. Turned out that the electrical tape came off and the resistor was touching metal and changing the resistance of the circuit. My worst case scenario thought was 'what if the VATS module gave out'. They are high and if you get one from the junkyard, you still have to find the right resistor to work which can be time consuming. The circuit is a nice idea if you want to get rid of VATs altogether. You'd just need the key to unlock the steering wheel to drive.

Ken

ringo234

I got tired of getting stuck waiting 5 minutes try again. I even had to be towed home once. I measured my key, soldered in equivalent resistor(s) and had a real security system installed, problem solved.

MrDude_1

without VATS, the common car thief can take your car in under a minute.

pull the window back (no window frame) and unlock the door.
bash the column open. that locking pin pops out, and you can turn the ignition switch to run.... push the starter button and drive away.

Blue1989RS

If someone wants your car bad enough, they will take it anyway, regardless of the preparations you've made. VATS just makes it harder. It would be just as easy to make a custom ECM, break into the car, swap ECMs and drive off.

I like the 555 timer circuit. Its simple, reliable, and bypasses the VATS module completely.

Keep in mind the ONLY reason you would want to bypass the VATS system is if the following happens(ed):

1. The pellet in the key doesn't work for any reason
2. Your VATS module broke and you don't want to buy a new module
3. You did a motor swap and don't have a VATS module

I just did number 3 to both my camaro's. One has the VATS disabled, the other has a hacked up resistor bypassed VATS module.

Dale

iTrader: (12)

Had another thought.

Put that somewhere where you have access to it. Put a quick connect between that and the harness. You go somewhere you dont trust, pull that out and take it with you.

I remember reading a thread on here(or maybe another car board) people would rig up things like the headlights had to be on to start, or wipers, hidden switches, etc.

MrDude_1

heres how i read that list.

1. you just need to get a new key made... yea its $35, but thats cheap for a good passive security system.
2. you're lazy. fix your car correctly, or spend the same amount of energy/time bypassing it.
3. the motor/ECM has nothign to do with VATS. even if you dont touch the system, and pull the motor or swap it...the starter disable still works. i have had a L03, 400SBC, and the current LS1 in this car, and the VATS still works fine.

Dale

iTrader: (12)

What hes saying is putting an LT1 or LS1 into a ride that never had vats to begin with. You either have to install the vats system, or install one of these boxes.

Your 91 had vats, so you can easily wire that into your LS1 system. Try installing that LS1 into an s10 or 69 camaro.

Blue1989RS

I like those hidden switch idea's. My friend used to have an RCA plug poking out of his dash and the mating end on his keychain. If it wasn't plugged in, the started relay wouldn't enable.

Here's one for you Mr. Dewd.

What if you are trying to put a TPI motor in a pre86 chassis (without VATS) and all you have is the engine side harness. Huh?

MrDude_1

ive put one in a 55 chevy, and im putting one in a non-vats thirdgen...

im capable of any number of solutions.. for example i can:
1. adding VATS to almost any GM car... the lock cyls interchange in most cases easily... and i understand the wiring.
2. remove VATS from the PCM.. using HPtuners, or EFIlive i can just flash the PCM to not require it... or in the case of a GMECM, i can just burn a PROM. in most swaps a "tune" of some sort is required anyway.
3. i could build that box, but add in a circut that required a specific resistance.. and make that resistance the key.... although that would be pointless because i can just wire in a GM unit pretty cheap.

simple.
take a VATS module, a relay for starter disable, a new key lock cyl, and a GM VATS key, and wire it in.
i could draw the schematic off the top of my head, but realistically, you're just being sarcastic, so i wont waste my time.

in anycase, there is another option makes much much more sense.
you probably dont want the stock spark tables. you probably arnt even running a stock motor. you may want to remove the air pump, egr, or modify a number of other small things.... in any of those cases, it involves burning a new prom (or having one made).... in that case, just have VATS turned off... simple, and you're not dependant upon some home brew circuit.


eliminating VATS when you have it is stupid.
the decision to go thru the work to add VATS is very debatable... its a PITA to run the column wires, and i cant blame anyone for not wanting to do it.... but then again, the best choices for our cars are not always the most fun things to do.

Dale

iTrader: (12)

1. What about one that doesnt interchange? Or for someone that has the tools to change a cyl out? (just for entertainment reasons, what would you do then?)
2. From my readings 3 years ago, there was no ecm crack/hack for the L32 harness which I put in my s10. ECM was the way I wanted to go. (there is one for the lt1 and ls1, yes)
3. Agree, making a specific resistance is kinda pointless.

MrDude_1

1. then you disable it in the ECM/PCM... as for the tools, if its a GM column, your local autozone rents them for free.
2. the 2.4 V6? yea, thats totally hacked as far as i know..... btw, on the newest motors, you have to do it in the ECM.. its serial commucations, not a pulse signal.
3. yea... i was just throwing it out there.

Dale

iTrader: (12)

2. L32 is a 3.4l, and as of 3-4 years ago, it was not hacked.

Grim Reaper

Another problem, IF you disable your anti-theft device AND your car is stolen, your insurance claim may be denied.

Remember this about Insurance Companies, they make money only two ways: 1) Increasing premiums and 2) Denying claims. Disabling a proper anti-theft device may turn you into "Catagory 2".

ringo234

If they try to open my door the Alarm will go off (very loud). I will be paged if I'm within a 100 yards; my ignition is disabled not by VATS but by my aftermarket Autopage Alarm System.

Vats didn't stop them from ripping my Console to pieces or from tearing my Steering Apart to try and steal my car. They did steal my radio though.

Check out this site:
http://www.joestradingpost.com/vats/

That's what the Corvette Forums think of VATS.

rodsatheart

iTrader: (1)

It works !!!. So nice to have the car running again.

c0wcommander

Sorry to bump back this old thread, but where exactly does the "output to ECM" wire plug into in the ECM?

Six_Shooter

iTrader: (2)

It would be the "VATS" or "Fuel Enable" input on the ECM.

mauricioboom

I've been searching for days for those schematics, my vats system gave up and won't read my resistor from the bypassed key. do you know if I will have to build the 30hz wave?. I have a 92 camaro and the box says passkey, the passkey on my 93 camaro says paskeyII, so they are different. Is there another way to generate the wave(using less components(diodes,resistors,capacitors etc)), and is there a way to measure the output wave if no occiloscope available?, let me know.

dunkirk

They will only know if you tell them???