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How to determine which VATS chip your key has.


VATS stands for Vehicle Anti-theft System and is also known as PASS-Key (PersonalCK595512 595525 Automotive Security System). Each VATS key has a resistor embedded within the key-blade, and each resistor has 1 of 15 possible values. Sometimes the resistors are refered to as a Vats Pellet or Vats Chip. Decoding a VATS key is very simple, but it requires that you know how to use an ohm meter. Any multimeter will have an ohm meter and any Radio Shack, Electronic or Hardware Store can sell you one.

CK596772 596785All VATS keys have a resistor embedded in the key blade with metal prongs protruding out of each side of the key blade. In order to read the resistance of the resistor in the key blade, place one lead of the ohm meter on one metal prong, and the other lead on the other metal prong, opposite, on the other side of the key blade. With the leads in their proper position a resistance value can be read from the ohm meter.

The value from your ohm meter will probably not match, exactly, the resistance value in the chart below, but choose the value closest to the value on your ohm meter. The corresponding code number is the identification number of your VATS key.
  1. Go to a Radioshack or other electronics equipment store and use a Digital Multimeter.
  2. Switch it to measure Kilo-Ohms (resistance.)
  3. Take the ends of the terminals of the tester and place them on the metal thread at the center of the VATS chip.
  4. Measure the Kilo-Ohms.  It will be between 0 and 12.
  5. Use this chart to decide which VATS key chip # you need.  Round your number to the nearest value on the chart to determine which VATS chip number your key has.

VATS Chip Number

1 0.402
2 0.523
3 0.681
4 0.887
5 1.130
6 1.470
7 1.870
8 2.370
9 3.010
10 3.740
11 4.750
12 6.040
13 7.500
14 9.530
15 11.801


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What is a transponder key or chipkey?


A transponder is a benign electronic device implanted in the head of a key which remains dormant until awakened by energy derived from its close proximity to an induction coil at the threshold of a vehicle’s ignition lock. When a transponder becomes energized by the ignition lock being turned ON, it transmits a unique Alpha-numeric identity code back to the induction coil and the on-board computer - for comparison with values stored in the computer’s memory. If the RF transmission from the transponder is an exact match then the engine can be started.

Transponder technology represents a major advance in theft protection.  Since its introduction in 1996, transponder key use has grown to over 90 million cars in North America today.

Transponder keys may also be called “chip keys”. Transponder keys are automotive ignition keys with signal-emitting circuits built inside.

When the key is turned in the ignition cylinder, the car's computer transmits a radio signal to the transponder circuit. The circuit has no battery; it is energized by the radio signal itself. The circuit typically has a computer chip that is programmed to respond by sending a coded signal back to the car's computer. If the circuit does not respond or if the code is incorrect, the engine will not start. Many cars immobilize if the wrong key is used by intruders. Chip Keys successfully protect cars from theft in two ways: forcing the ignition cylinder won't start the car, and the keys are difficult to duplicate. This is why chip keys are popular in modern cars and help decrease car theft.

Many people who have transponder keys are not aware of the fact because the circuit is hidden inside the plastic head of the key. On the other hand, General Motors produced what are known as VATS keys (Vehicle Anti-Theft System) during the 1990s, which are often erroneously believed to be transponders but actually use a simple resistor, which is visible in the blade of the key. If the value of the resistor is wrong, or the key is a normal key without a resistor, the circuit of the car's electrical system will not allow the engine to be started.

How Transponder Works



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