Citroen use a unique reference code for each XM key. This is listed in the original vehicles documentation. From this code a few Citroen dealers will cut keys to order and Citroen will supply new keys and locks to special order.
If the code for your locks has gone missing this self help will explain how to measure a key blade to reconstitute the code number. Even if you have a record of the code it is as well to check it against a working key before ordering. Car locks do get changed for various reasons and there is always a risk that the new code does not get recorded in the vehicle history.

The key blank for an XM has a cruciform cross-section to the blade measuring 8.10mm across the wide part of the cross and 4.15mm across the narrow part. Two types of key blank are available the difference being the plastic head to the key. The SX9 type is a standard key plastic head. The other type is a small plastic section to fit in a plip. This plip key will fit either Mk1 or Mk2 plips.

Key Blade Dimensions when cut:

A cut XM key is actually two identical sets of notches 180 degrees apart so measuring with calipers across the key in the notches allows you to calculate Citroens key code. There will be up to 4 matching pairs of notches on the narrow part of the cross and up to 5 matching pairs of notches on the wide part of the cross. I used the term "up to" as on some key blade positions a full key cross section may be used to operate a key tumbler so that that bit of the key cross-section is missing its notches. The notch positions are equally spaced down the side of the cross but there is an offset between the wide and narrow sets of notches. There is also a critical dimension between the point of the key and the notch positions. A locksmith with general purpose key cutting machines will have to correct these dimensions manually four times to cut each side of the key correctly.

Narrow side of cross

Code -- Dimension
The deeper the cut the higher the letter.
A -- 4.15mm
B -- 2.98mm
C -- 1.86mm

Wide side of cross

Code -- Dimension
The deeper the cut the higher the number
1 -- 8.10mm
2 -- 7.20mm
4 -- 6.20mm
6 -- 5.20mm
8 -- 4.20mm


Measurement starts at the notches nearest the head of the key and progresses a notch at a time towards the point.

This will give you a sequence of 4 letters followed by 5 numbers.

An example might be: A C B B 2 1 4 2 6

The 4 letter part of the code now needs to be converted to a 2 digit number.

Letter conversion table:

AABB - 01.. ACAB - 12..BABC - 23..BCAB - 34..CABC - 45..CBCC - 56
AABC - 02..ACAC - 13..BACA - 24..BCAC - 35..CACA - 46..CCAA - 57
AACB - 03..ACBA - 14..BACB - 25..BCBA - 36..CACB - 47..CCAB - 58
AACC - 04..ACBB - 15..BACC - 26..BCBB - 37.CACC - 48..CCAC - 59
ABAB - 05..ACBC - 16..BBAA - 27..BCBC - 38..CBAA - 49..CCBA - 60
ABAC - 06..ACCA - 17..BBAB - 28..BCCA - 39..CBAB - 50..CCBB - 61
ABBA - 07..ACCB - 18..BBAC - 29..BCCB - 40..CBAC - 51..CCBC - 62
ABBC - 08..BAAB - 19..BBCA - 30..CAAB - 41..CBBA - 52
ABCA - 09..BAAC - 20..BBCB - 31..CAAC - 42..CBBC - 53
ABCB - 10..BABA - 21..BBCC - 32..CABA - 43..CBCA - 54
ABCC - 11..BABB - 22..BCAA - 33..CABB - 44..CBCB - 55


So in the example above: A C B B becomes 15

So the key code for replacing that key is:-- 15 21426

Regards

John

This post has been edited by xmexclusive on July 23, 2008 09:14 pm