Information: Alarm Transmitter Coding
Models: 1991 thru 1993 164 Vehicles
Date: 04/12/95
The ALARM ECU is located in the trunk, on the left rear wheel well, under the carpeting. It is designed to recognize a RF (Radio Frequency) code sent by the remote transmitter.
The RF code number can be found printed on a sticker; 1 ) inside the remote transmitter, or 2) inside the alarm ECU.
The RF code is made up of the letter "A" & three digits, plus the letter "B" & three digits example A227B264.
A remote transmitter can be programmed or "coded" by opening the case, removing the circuit board and bridging the appropriate chip pins to a solder strip using a low wattage soldering iron.
There are two solder strips, one for the "A" code Iouter strip· and one for the "B" code (inner strip).
Each chip pin has a numeric designation that, when choosing the proper ones, will numerically add up to the code. See page 2 of the bulletin for an example of how to decipher a code.
To determine which pins should be "bridged" you must perform a series of mathematical calculations. The results will indicate the appropriate pins. See page 3 for remote transmitter circuit board diagram.
FOR EXAMPLE: Code A227 8264 as in figure 2
Starting with the "A" part of the code (227).
FIRST TAKE 227
subtract the -128 Note: 256 is the largest pin #,
largest pin # 99 but, cannot be subtracted
from 227.
THEN TAKE 99
subtract the -64 Note: could not use 256 or 128
largest pin # 35 cannot be subtracted from 99.
THEN TAKE 35
subtract the 32 Note: could not use 256,128 & 64
largest pin # 3 cannot be subtracted from 35.
THEN TAKE 3
subtract the -2 Note: could not use 256,128,64,32,16,
largest pin # 1 8 & 4 cannot be subtracted from 3.
THEN TAKE 1
subtract the -1 Note: could not use 256,128,64,32,16,8,
largest pin # 0 4 & 2 cannot be subtracted from 1.
After you have broken the code down to "0"; you will solder the pin numbers that you identified using the above subtraction method, to strip A or B. Obviously use strip "A" for the "A" code & strip "B" for the "B" code. In this case you would solder pins 128, 64, 32, 2 & 1 to strip "A". Repeat this same mathmatical procedure for the "B" part of this code. In this case you would find that B264 would break down to pin 256 and pin 8. You would solder both of them to strip "B".
Note: You must subtract the largest possible pin numbers until you break the code # down to "0". If your math calculations do not result in "0", your calculations were incorrect or you do not have a official code number.
Note: A chip pin number will never be used for both "A" & "B" strip on the same circuit board.
Figure 1 shows the back side of a new non-coded transmitter circuit board.
Figure 2 is an example of a transmitter with soldered bridges that make up the code A227B264. EXAMPLE CODE: A227B264
Remember! A chip pin number will never be used for both "A" & "B"
strip on the same circuit board.
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