You need the supplement to the Service manual. You have the regular book, the LT5 book and then there is a electronics book which has the FX3 in it.
Here is some of the codes
12 = Start of sequence
13 = Left rear time out
14 = Right Front time out
21 = Left Front time out
22 = Right Rear time out
31 = Left Front out of position
32 = Right Front out of position
33 = Left Rear out of position
34 = Right Rear out of position
Out of position codes are triggered if the computer senses that the actuator has not found the end stop position on the shock. Remove actuator at the indicated shock. Turn the valve gear on the shock stops after about 3 / 4 of turn, then you have a bad actuator. If it spins around continuously then it is a bad shock
41 = Selective ride control switch short to voltage
42 = Selective ride control switch open contacts
You can have a code 42 if you leave the switch in between indented positions
43 = selective ride control switch circuit open.
Oh and if you need replacement parts, there are two different sets of FX3 gear 89-91 and 92-95. They are not interchangeable
To contact Bilstein for repairs
The guy I talk to is Bill Hendorf. Great guy.
The address for shipping the shocks
Bilstein Repair Dept.
14102 Stowe Dr
Poway, CA 92064
Make sure you enclose your contact info so they can get ahold of you to verify what you need done and also charges incurred durring the repair.