# Can the lost ignition key code be decyphered from an old key?



## montreal-1 (Apr 20, 2006)

Hello,

My wife bought her '98 Sentra second hand and was never given the X-code (blind code) that corresponds to her ignition key.

The manufacturer has no record nor the dealership which first placed the car in service.

Her keys are beginning to stick a bit in the lock cylinders and we would like to generate new masters if only we had the X-code or the bitting code which is what the locksmith eventually uses to setup the cutting machine.

I don't want to remove any cylinders from the car in order to have a locksmith determine the bitting code.

I am wondering if the bitting code can be reversed engineered by measuring the varius notches on the old keys with a micrometer.

Even with an allowance for wear on the old key, the widths as measured should allow one to conclude what original bitting code is the closest match to the worn key.

Thanks for any information.


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## montreal-1 (Apr 20, 2006)

The answer to my question appears to be yes.

After my favorite locksmith claimed that my key would be too difficult to measure for a number of reasons, I re-contacted my local Nissan dealership who said that there are 8 digits in the bitting code and there are only 4 possible numbers for each digit, namely 1,2,3, or 4.

A value 4 corresponds to the deepest notch cut into the blank key and value 1 corresponds to the minimum notch depth.

Between value 1 and 4 is 57 thousands of an inch, or 19 thou per value change.

In order to help me read my bitting code off my old key, my Nissan dealer cut me a special key with code 43211234 cut on one side and 12344321 cut on the other side. This particular combination helps to identify the horizontal spacing and the vertical notch depth.

Because the steps are cleanly layed out on the special key, it is easy to hold the special key against the old key and see where the old key's peaks and valleys line up with respect to the steps on the special key.

I used a micrometer to measure notch depth, but given that there are only 4 notch depths with the maximum depth (value 4) coinciding with one of the longnitudinal grooves in the key shank and the minimum depth (value 1) coinciding with the first minimal step down from the handle, it is not hard to estimate which notches correspond to values 2 and 3. My key used all four notch values, and one particular value was used only once and another was repeated four times.

Once you have determined your bitting code, you can take this code to your Nissan dealor and have a new master key made. Just identify whether the first or last of the eight digits goes closest to the point of the key, else the digits may end up being fed into the cutting machine in reverse order.

It would be nice if there was an algorithm to convert the 8 digit bitting code back to the original 4 digit blind code (ex: X-1234) which came with the car. It is probably easier for any locksmith to make a new key with a blind code compared to a bitting code.

As I stated above, the difference in notch depth between successive values was about 19 thousands of an inch on the special key. My wife bought her 1998 Nissan Sentra second hand without any master key, so the only keys we have were in use for over 6 years.

On her oldest key, the difference in notch depth between successive values varies between 17.5 and 26.5 thousands of an inch, which is different from the nominal 19.

For this reason, I did not want to cut an identical duplicate of her old key and apply the same errors. 

Creating a new master with the bitting code allows the pins in the lock cylinder to function almost the way they did when the car was new. I assume that the key has worn faster than the pins in the cylinder, but even if the wear on the key notches and the cylinder pins has been the same, the pins will still work better with a new master key than an old key..


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