aloa.org June 2024 Keynotes 33 car has a dead battery. The mechanical key rarely gets used at all, which means the locks don’t get much wear, either. Key interchange in automotive locks is becoming a thing of the past. What to Do Today But there are still many millions of older cars on the road that are vulnerable to key interchange. We can take advantage of this when making keys. This could help us in the case of a badly cut key or a broken key, or a key that is severely worn. This can even help if the key is lost entirely. First, consider a broken key. The older the key is, the more worn it gets. Broken keys often result from people abusing their keys. Sometimes the tip of the key will be stuck in one of the locks, or it may be lost. But even half a key still gives you more information than if the key were lost entirely. Consider a badly worn key. Often, the wear is so bad that you may have great difficulty measuring the key. Cuts which were originally 1s and 2s can be worn down almost as deep as 3s. The key keeps working because the locks wear out too. The first sign of trouble might be that the key no longer works in the passenger door (the lock which has the least amount of use and hence the least amount of wear). In the case of double-sided keys, the customer may find that the key works if oriented one way but not if it’s upside down. Whether it’s a broken key, a bad key, or a lost key, the job is pretty much the same: reverse engineer the bitting of the key and cut a key by code. In many cases, you can take advantage of key inter- change to help you find the right key. The easiest way to cut a key by code is if you know the key code for that par- ticular vehicle. You might get the key code from a dealer, or you might find it stamped on one of the lock cylinders. Then you can look it up in your code software. But let’s assume that you don’t have the key code in hand. The code soft- ware will still be very helpful. Example 1: 1989 Chevy Astro With a Lost Ignition Key For this example, I’ll use tryout keys, special keys that are cut to half depths. They are the modern-day equivalent of true skeleton keys. They are never pre- cisely the same as the correct key, but they are close enough that they will turn with a little bit of wiggling. The entire set of tryout keys for GM six-cut has just 207 keys instead of 1,000. You go through the ring until you find the one that turns. Suppose it’s 1½ 1½ 3½ 3½ 1½ 3½. But remember, this isn’t the correct key! It turned because we are taking advantage of key interchange. It’s just very similar to the correct key. Unfortu- nately, it’s also similar to a couple dozen other keys, which would turn the locks in lots of other cars. Tryout keys (or cop- ies of them) should not be given directly to customers. Once you have determined which tryout key will manipulate the lock, the next step is to make a list of all the correct keys that are similar and test them until you find the correct key. The technique for this is called progression. You probably know progression as a way of determining a couple of unknown cuts when the rest of the cuts are known. It’s the same thing with tryout keys; we just have fewer choices for each cut. In the example I gave above, the last cut on the tryout key was 3½. If this key turned the lock, we would infer that the correct sixth cut is either a 3 or a 4. Here’s where the code software comes in handy. Rather than making a list by hand, we can ask the code software to find them for us. First, look up the year, make and model. Then search by cuts. In the search window, my favorite code program lets you put A if the cut is 1 or 2, but you aren’t sure which. Here’s the complete list. 1 or 2 A 3 or 4 B 5 or 6 C 2 or 3 X 4 or 5 Y 6 or 7 Z For our example, the tryout key is 1½ 1½ 3½ 3½ 1½ 3½, so I’d search for AAB- BAB. The software would tell me there are 14 matches. Here they are: 113313 113324 113423 123424 124313 124324 124423 213323 213424 223313 223324 223423 224323 224424 The great thing about this is that the code program has already checked for MACS violations and weeded out the keys that aren’t in use (due to having the wrong parity). Even better, I could ask the software to rearrange them in progression order, to minimize the number of key blanks I need. Here’s the reordered list, separated by horizontal lines where continuing would require a fresh key blank. 113313 113324 Tryout keys (or copies of them) should not be given directly to customers.
