2003 Security System Questions

JimG563

New member
2
1
1
Chicago, IL USA
Buick Ownership
2003 Century Custom
I recently bought a 2003 Century Custom used. The vehicle has barely 60K miles on it, and so far runs pretty well. I have a couple questions and an issue with the security system:

1. I only have one set of keys, and no remote key fob. I can locate a Buick dealer in my area - it's just a pain that the ignition key is chipped.

2. I've had three real recent instances where the car won't start when I turn the key, and the SECURITY light flashes. I have to wait and and try to "fiddle" with shifting in and out of park to engage and release the door locks several times to get the car to start.

How does the non-start thing happen, and what can I do to either bypass it or fix it?
 

Thunderhawk09

Member
63
10
8
Buick Ownership
2001 Buick Century Custom & 2005 Buick LeSabre Custom
If you have a 1996-2005 GM vehicle without the chip in the key and are having trouble starting the vehicle CLICK HERE With that out of the way, here's an explanation of the VATS system (which I culled from a locksmith selling VATS blanks on eBay.) WHAT IS VATS? Vats stands for Vehicle Anti Theft System. Lots of people refer to this type of key, as a " computer Chip key". This key or "Chip" has nothing to do with a computer, nor is it a chip. But because of the popularity of calling it a computer chip key, so will we. So that we don’t confuse. The black chip on the blade of the key, is actually a resistor. GM first started using the Vats key in 1986 on the Corvetts, then some of the Cadillacs, ect. GM uses 15 different resistors in their VATS keys. Just by looking at the keys you can’t tell the difference. How does the VATS System work? Each VATS key has it’s own unique cuts on the key to operate the lock. but the cuts alone will not allow the car to crank. This is called a mechanical key. Each car has a VATS module (Brain) under the dash that communicates to the starter, fuel pump, and the ignition lock. Each VATS module is randomly given a # (value) from the manufacturer. When the proper mechanical keys, along with the proper VATS chip (resistor value) turns the ignition lock, the VATS module reads the chip on the key . If it is the correct chip, the VATS module will tell the starter and the fuel pump to operate. If the wrong chip is read, the VATS module will tell the starter and the fuel pump to shut down. How to determine the Value of your key: By chance you may know what VATS key you now have. Most people do not. There are basically two ways to determine what VATS key you have. Remember, there are 15 differrent possibilities. First, your key can be "read" in a VATS tester. Most locksmiths have these readers, and don’t change anything to tell you. There is another way for you to read the key value yourself. If you have a Volt Meter you can test the OHMS (resistance value) of the chip yourself. Just set your Volt meter to check OHMS, take each lead and place it on each side of the "chip" on your key. A number will appear. Take that number on your volt meter and apply it to the OHMS chart below. Keep in mind that it may not be exact. Just pick the closest value to your reading. This chart is for any GM product, Buick, Cadillac, Oldsombile, Chevrolet, and Pontiac that has a VATS key (single or double-sided.) VATS # (K)OHMS (Set your meter to the 20k ohm setting)
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
You can bypass this system by using a combined resistor value that equals the resistance of your VATS key like mine wound up being a number 15 which to get my resistance I had to use a 10k ohm 1k ohm and a 800 ohm

You can bypass the vats system by finding the two wire harness coming off ignition key switch it will have a connector that plugs into the multi function switch cut the harness on the upper side of the connector between the key switch and connector you can tie your resistor or resistors in series and tie the resistors one end too each wire this will need to be done to the end with connector not the end coming from switch

It doing this because the switch contacts are worn and not always making contact with the resistor you can replace the switch or my preference bypass the crap all to together as refereed to above

A way to check for sure this is the issue is find the two wire connector from switch unplug it and check ohms resistance between the two wires from switch and repeatedly remove key & reinsert key if at any of the time you reinsert key your not getting a reading that is your problem
 
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Zeroboostbuick

Well-known member
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83
S.W. Ontario Canada
Buick Ownership
2018 Regal Sportback - 2010 Yamaha R6 (track bike) Past cars: 92 LeSabre, 98 Regal, 02 GrandPrixGT

Thunderhawk09

Member
63
10
8
Buick Ownership
2001 Buick Century Custom & 2005 Buick LeSabre Custom
I'm in Canada and some Car Part stores and some locksmith shops cut those key's with the chip and VATS system.

They test the resistance of the key and get one the same and cut it. Very cheap too.

There is a procedure for the car owner do to re-program a new key as well, but if the new key has a different resistance then the original then the original will no longer work.

Edit: WHY IS SOME OF THE STUFF I WROTE GREEN ???
Yeah but the problem is more than likely in the switch contacts and to me it better just to bypass so that is why I gave the info to do so and from what I have read the VATS system can not be programmed it uses the resistor key # that car came set with or nothing
and to me the price of a locksets then having car re keyed so same key still works both doors and ignition it not worth it for a car that now is only worth a few grand bypass it and forget it
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2007LucerneCXL

Full Member
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725
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Illinois
Buick Ownership
2007 Lucerne CXL. and 1995 Lesabre currently, past 1973 Riviera, 1968 Riviera
Thanks for the opt out, it or the forum was changing some links I posted to dead ones hopefully this will cure that for mine.
 

Thunderhawk09

Member
63
10
8
Buick Ownership
2001 Buick Century Custom & 2005 Buick LeSabre Custom
Thanks for the opt out, it or the forum was changing some links I posted to dead ones hopefully this will cure that for mine.
Yeah I done all of the above for mine and they finally went bye bye for me I never knew that was related to my computer till it happened in that other forum and they set me straight now I know
 

ledzilla

Full Member
200
14
18
Buick Ownership
2001 Century Custom
I've had this happen a few times, but not for quite a while, thankfully. Good to know. Thanks for the info.
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