GM Key Blank Info

Paul Steinberg

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GM used the same key blank groove configuration for both the ignition and trunk / glove box from 1935 to 1966. Starting in 1967, in an effort to combat auto theft, they change the groove configuration on both the ignition and the trunk to be separate grooving. To add to that, they also added a letter code to designate each of the key blanks. Below is an explanation of the years that each letter code designation correlates to.

The 1967 & 1968 GM keys continued to use the standard hex & pear shaped keys, even thought they changed the keyway configuration for each year.

1967 = A & B Keyways
1968 = C & D Keyways

Starting in 1969, GM changed the head of the key to a larger square, and a rounded top square for the door and trunk key. This was done because of
the introduction of the steering column ignition and lock. The new square & round top keys fit the following years.

1967 1971 1975 1979 1983 1984 1985 = A & B
1968 1972 1976 1980 1987 1988 1989 = C & D
1969 1973 1977 1981 GM Key = E & H
1970 1974 1978 1982 = J & K

First implemented in 1986 by General Motors, VATS keys were originally only for the Corvette. They were later used for the Cadillac and its future models. A VATS key, (VATS standing for Vehicle Anti Theft System,) is a key often referred to as a 'computer chip key.' These keys need to be programed by a locksmith or the GM dealer. If you loose one of these keys, it can get very expensive to have them replaced. In some cars, if you have 2 original keys, you can have additional keys programmed using these 2 keys and the special codes that allow it to be programmed using the cars computer system.

I found some key pictures on eBay so you can see the various keyways used for the various years, and how they differ. The keyways also changed on the backside of the key, so you couldn't put a "wrong" year key into the lock. This is just an simplified overview and there are other "factors" that come into play, such as the key cuts themselves being proprietary to each year. Unless you want to become a locksmith, it is more information than you need to know.
 

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Good information. I have one of the 1970 J keys on my desk at work, from a 1970 coach I bought when I was much younger. I was young and got lied to/screwed over, so I keep that key as a reminder. I do have the code for 1968 if anyone ever has the need
 
If I may elaborate a bit on the "chip keys".

The original "VATS" key, or wafer chip. There were 15 different chips, resistors actually. VATS were read through the ignition lock cylinder. The chip was determined by a VATS module, located under the dash panel. From inception to about 1989 or 1990 there was no way a dealership could access the VATS code, the module either had to be removed and checked for the code inked on it or a VATS decoder box was plugged into the car's lock cylinder circuit, now a trial and error. It had to reset each time, I forget exactly how much time but if memory is correct it took about an hour and a half to go through all the codes. Finally GM started recording the VATS code on the factory records with the key codes, but we still had charts to decode the VATS as it was "encrypted" with letters instead of the numbers.

Also, for you with VATS keys, record your key numbers or make sure you have at least one spare ESPECIALLY if you have to replace the lock cylinder as there are no numbers stamped on the case. If you buy a new GM cylinder, not sure on the aftermarket ones, but GM included a "work key", it was a cut key in brass with the code stamped on the top of it. THAT IS YOUR ONLY RECORD for the replacement key. If you lose it, you will be calling a locksmith or replacing it again. And those did not have wafer chips, again the chip was determined by the VATS module under the dash, not the lock cylinder. Another way to identify those is the key is a single cut. there were a few double sided keys but those were Buick Regals only IIRC,

Now to the double sided keys. There are ones with no security chip, mainly light and medium trucks with a few oddball cars in the mix. Identified by a shank/blade with no markings beneath the plastic head covering on the shank (teeth area). They have a basic security system built into the ignition cylinder, sensors have to line up by turning the lock cylinder with a key or no start (usually).

Now to the double sided security keys. Two types, both look similar to the unchipped key. The "chip" is in the head under the plastic. First type is the "PK3" which stands for passkey 3, now letters stamped on the shank just below the key head. Now a reader by the lock cylinder receives a code from the key, vehicle has to be "taught" to accept the key, wrong key or no coding set, no start. Second type is the "circle plus" a circle with a plus sign in the center, again same place as PK3, same principal. THEY ARE NOT INTERCHANGEABLE, PK3 will not start a circle plus and visa versa. No bueno!

Unlike a VATS, the new key comes blank. You can add up to ten keys to one vehicle, as long as you have at least one key you can program the new keys, takes about thirty seconds. Insert the existing key, turn the ignition to "on" without starting it. I usually waited until the seat belt chime turned off. Turn off, remove "old" key, insert new key, same procedure. Now when the seat belt chime turns off, rotate the key to off and now try it, it should work.

If you lose ALL KEYS, the fun begins. Now you start from scratch. You get a key from the dealer cut to your code. You now insert the key, turn it to "on" and walk away for ten minutes. Come back, turn "off", turn back on for ten minutes. This has to be done three times. After the third cycle, turn off then try it. Should work. Valuable lesson, always have at least two keys for your car, the area I worked in, the people never learned. I had a couple of "frequent flyers", once a month the dummies would come in, get one copy of the key and go through the programming only to lose it and repeat the cycle the next month.

There are some variants, some of the GM keys even though the catalog said that they were correct they would not work, keyway wrong, shank length wrong or thickness wrong. A good GM counterman will be able to figure out what it will take, Ebay sellers, you are on your own.

That brings up another thing, those keys off Ebay sometimes did not work for various reasons noted above. Sometimes the car would not accept the key's anti theft sensor. Sometimes the seller would send a PK3 instead of a circle plus or send a non security key. Buyer beware. Depending on the customer's attitude I may or may not charge them to cut their own key, the key cutter cost the dealerships 5-6k plus maintenance and replacement parts, somebody has to pay for it. Also I always informed a customer that I would cut it to the code or to the old key supplied but if the key did not work vfor any reason I was not responsible for replacing it. The quality of some of those keys was appalling, mainly from overseas.

Sorry to drone on for so long, but it was a long story........
 
If you buy a new GM cylinder, not sure on the aftermarket ones, but GM included a "work key", it was a cut key in brass with the code stamped on the top of it. THAT IS YOUR ONLY RECORD for the replacement key

Forgot to say, the work key is a brass dummy with no wafer chip. the wafer chip is determined by the resistor needed to complete the circuit in the VATS module so each time you replace the ignition lock cylinder unless you are very lucky and the old key has enough "meat" on it to recut it to the new code you will be also buying a couple new keys as you cannot disassemble those lock cylinders and recode them at least under normal circumstances. Probably somebody can and while I could recode some cylinders the way those were staked made it impractical for me to try. Not to mention the very thin white and orange wires from the resistor reader, those breaking were a major cause for those locks to be replaced.
 
now just when you think you have all the answers along comes a car to prove you wrong. there are three sets of the keys for the 72 CB there were 2 sets of square keys on me other one also. I just figured someone has changed the switch. but when we changed the radiator on the limo style one I found a set of keys wired under it with the dealers key fob. they were new cut and had never been used. this car has the C key for the switch the D key for the glove box and a A key for the locks. I'm going to try the d key in my other one and hope. as the latch is loose and you can't tighten it with out a key
 

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Ed, your CB brings up another thing.

I may be wrong here as I have never pulled up a key code for a Cadillac Commercial Chassis so I'm using my experience from other GM vehicles.

On late model key inquiries and all factory invoices I have seen there were only two key codes, one for "Ign" and one for "Trk" except for 90 (?) and later VATS cars the two letter code for the two digit chip number. So I'm assuming that the body builder was installing it's own supplied lock cylinders for the doors. Briggs and Stratton was the OEM supplier for lock cylinders at that time and I imagine GM authorized them to buy OEM branded lock cylinders coded in sets from them.

From 1967 through 1973 GM ignition lock cylinders and door cylinders were the same key (square), trunk, glove compartment and console if so equipped were keyed the same (oval), you could leave your ignition key with a parking lot attendant and still have your trunk secure from them.

Starting in 1974 the ignition (square) was only used for the ignition, the oval was now for the remainder of locks, it was said at that time it was an anti-theft reason. I think the real reason was that it was cheaper for GM to buy the ignition lock cylinders precoded in bulk from B&S instead of coded for production and uncoded for service replacements. Then in 1978 a new more theft resistant ignition lock cylinder was released. The original 1969 to mid year (?) 1978 cylinder was retained in the ignition lock bowl by a small spring bar, not too resistant to slide hammer pullers. The second design 1978 cylinder was retained by two machine screws, more resistant to theft but still could be defeated by determination.
 
CB probably specified the square head key to be coded with a different keyway so the wrong key could not be inserted into a lock cylinder and twisted off in a adrenaline fueled rush.

Some later GM cylinders, mainly doors were universal keywayed so GMSPO could stock fewer cylinders in their system, fits all for lack of a better description.
 
One never knows what the aftermarket manufactures did. I'll try the keys in the other 72 the door locks might be all the same. Just the switch key different. On the Oldsmobile. Some of the caddys I have had here were switch key and door key same. but I was not paying attention to who built the car. Might be one other way the lines were different.
 
My 1969 Miller Meteor ambulance uses one key for both the doors and the ignition switch. The glove box is a separate key. Door locks are all stamped with the key number, and I assume the same for the ignition lock.
 
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