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HOW TO: VATS bypass method

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This is my VATS bypass method. It's a modified method from what I found here: http://vats.likeabigdog.com/ I'm writing this up because the method of splicing in didn't work for me and I came up with a slight alternative.

This is a rough 1st draft. I will try to get some photos done soon, the photos I originally took didn't turn out very well.

Suggestions on clearer wording, errors, improvements or tips are appreciated!

The updated version with pictures will eventually be kept here: Easy Passkey Bypass

Symptoms:

Your car won't start. There is no sound from the starter engaging.

In older model Cadillacs like my 1990 Coupe Deville:

Your SECURITY light might light up, and the starter will not engage or make the usual cranking noises. In my specific case, the SECURITY light did not light up, instead it turned off when turning the key.

In newer model Cadillacs like my old 1995 STS, you will receive the following message on the dash:

Starting Disabled Due To Theft System

Wait 3 Minutes

...

Wait 2 Minutes

...

Wait 1 Minute

...

Start Car

Background:

VATS stands for Vehicle Anti Theft System. The security system in some GM vehicles uses a key pellet to prevent auto theft. The car's computer looks for the resistor pellet to be present, and will not start the car if the resistor pellet is missing or out of range. The very thin wires inside the ignition wear out and break after many turns of the ignition key, causing the car to not start. We are going to be bypassing those thin broken wires. This will make your car easier to hotwire by bypassing the ignition cutoff, but your alarm system and keyless remote will still work.

Tools needed:

A Multimeter

30 watt soldering iron

wire cutter and wire stripper

some solder

1/2 watt resistors adding up the the resistance in your key pellet

heat shrink tubing

about 6-12 inches of wire. 16 gauge works well.

A ratchet and some sockets

Step 1: Determine the resistance of your key pellet

Turn on your multimeter and set it to measure resistance (OHMS). If your meter is not auto-ranging, set it to the 20k setting. The black pellet on your ignition key has one wire on each side. Connect the red lead from your multimeter to one side, and the black lead to the other side. It doesn't matter which color goes to which side. Read the display on your multimeter and write down the number.

This chart is from my 1990 Cadillac factory service manual. It shows all possible values for the passkey system. Pick the closest value to what you wrote down.

KEY CODE : OHMS

1- 402 ohms

2- 523 ohms

3- 681 ohms

4- 887 ohms

5- 1,130 ohms

6- 1,470 ohms

7- 1870 ohms

8- 2,370 ohms

9- 3,010 ohms

10- 3,740 ohms

11- 4,750 ohms

12- 6,040 ohms

13- 7,500 ohms

14- 9,530 ohms

15- 11,800 ohms

Step 2: Visit Radio Shack

Cost for resistors and some wire should be under $15.

Head on over to Radio Shack and pick up some 1/2 watt resistors. Using 7,500 ohms (7.5k ohms) as an example, we will pick up a 5.5k pack of resistors, and a pack of 1k resistors. Resistors have a tolerance of 5-20%, so we're going to pick up some extra 100ohm resistors. 5.5k, plus 1k plus 1k should theoretically get us to 7.5k, but with a tolerance of 5% they might only add up to 7.2k. Therefore we use our extra 100ohm resistors to get us as close to 7,500ohms as possible.

The vehicle has some tolerance as well. Using our example of 7,500 ohms, if the computer sees 7,450 ohms or 7,550 ohms it should be within tolerance and work just fine. I believe the tolerance of the VATS system is 5%.

Step 3: Putting together the bypass wire

Plug in your soldering iron and let it warm up.

Take 2 of your resistors and wind them together. If you hold the wire leads at an angle you can wind/coil the leads around each other. The goal here is to have the 2 resistors in a line. Solder the middle of the winding to connect the resistors together. [Pictures here would help]

Once you have your resistors together, measure them with your Multimeter to make sure the resistance value is equal to the resistance value of your key pellet. If it's not, then add a 100ohm or 10ohm resistor to get it as close as possible.

Once it's as close as possible, solder on a couple inches of wire to each end of your line of resistors.

Next, take your line of resistors and wire and slide it into your heat shrink tubing. Using a lighter or heat gun, shrink the tubing to the resistors and wire. This makes it clean looking and also protects the resistors.

Step 4: Installing our bypass wire

There will be a plastic panel underneath the steering wheel where your knees go, and possibly a metal plate beneath that, depending on your car model. These should remove with your ratchet and sockets. You may need an extension to reach some of the bolts.

Once the panels are removed, we need to look for a flat orange wire. You will see it coming down from the steering wheel and going down the steering column.

There may be TWO orange wires on the steering column, so to identify the correct wire we follow it from the steering wheel down to a wiring harness connector near where the driver's left foot sits. The flat orange wire is actually a covering over two very small 22gauge wires, and you can see it split into two wires and go into this wiring harness. This identifies the correct wire.

At the steering wheel end of the wire, you are going to cut off the orange wire as close to the steering wheel as you can.

At the harness end of the flat orange wire, you are going to cut it about 6 inches from the harness. Discard the wire section that you just cut out. This will leave you with a 6 inch wire hanging off the harness. We are going to strip the end of this wire giving us access to the 2 individual wires inside.

Solder one end of your bypass wire onto one of these wires. Solder the other end of the bypass wire onto the other wire. Now, instead of one big loop going from the harness up to the ignition key resistor and back, we have a smaller loop containing our bypass resistors.

If this was installed correctly, your car will now start :)


WARNING: I'm a total car newbie, don't be surprised if I ask a stupid question! Just trying to learn.

Cheers!

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I was lucky to only need a 680 resistor....and at only .99 cents for a pack of 5! So....thank you sooooo much for this info...saved my day man!!!!!!!!!! :hatsoff:...by the way.....the orange wire with the two thin wires inside went to one large plug instead of a small two pin plug.

Edited by brcree

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