Replacing your siren batteries

The siren module contains 2 Lithium batteries that power the alarm siren in case a thief disconnects the car battery. Unfortunately, the unit is very sensitive to the voltage output of the batteries and demands replacement every 5-6 years. The symptoms of this problem include a "Service Theft Alarm" message on the SID and a car alarm that randomly goes off for no apparent reason.
The bad news is that a new siren unit costs around $240. The good news is that you can replace the batteries yourself in about 2 hours work!

Some of the tools required for this job are of the more advanced variety:

You can purchase batteries here for about $18 plus shipping. These batteries have the required legs already installed on them.
www.batterystore.com

Here is a link that doesn't require a minimum order.
Ebay store.

NOTE: These replacement batteries are not the exact same type that came in the module. These new batteries will get rid of the SID message and the false alarms, but will probably not be able to power the sirens if someone disconnects your car battery. I will update this link once a better replacement battery is found, but for now it is either this or buy a new alarm module.

The siren module is located in the left front fender. You need to jack up the car, remove the wheel, and then loosen the front of the wheel well liner. You do not need to remove the whole liner, as the plastic is flexible and you can work around it pretty easily.

The siren module is held on with one 10mm nut and one 10mm screw. Unscrew both of these and pull out the unit. Using a small screwdriver pull out the red tab to disconnect it from the car.

If you have a 1999 car, you now simply unscrew the six screws and pull apart the unit. If you have a later year car, it's time to get out the dremel and start cutting! I followed the lip all the way around. Be sure to wear safety goggles as plastic pieces will fly everywhere! If you haven't done so already, you should plug in your soldering iron to make sure it gets up to temperature.

Now split the unit apart. To remove the circuit board you need to pull off the remaining piece of the top piece. Once the board is removed, you can disconnect the two siren leads The last step is to disable the batteries by pulling off the red jumper.

Now using the sucking side of the iron, place it over the battery pins and suck up the solder. If you don't have this type of iron, getting rid of the solder on the pin is much harder to do and inserting the new battery into the hole is even more of a pain. Just spend the $25 at Radio Shack to pick up the special tool, it's well worth the investment.
Carefully pry off the batteries from the circuit board. Be careful not to damage the board with the screwdriver.
Place the new batteries on the board and using the regular end of the solder iron, solder the pins back to the board. The proper way to solder the pins is to first heat up the pin and board with the tip of the iron. This may take anywhere from 10-15 seconds. Then apply a small amount of solder to the pin and it should melt onto both the pin and the board. Do not apply the solder directly to the iron as this will only ball it up and fall off!

Replace the red jumper, reconnect the siren leads and insert the circuit board back into the module. To screw the pieces back together, drill out each of the six holes from the back of the top piece. Now insert the six screws into the unit.

Apply some silicon sealeant around the edge of the unit to keep out any water and dirt. I used a simple bathroom silicon sealeant. Unfortunately, it took about 48 hours for it to dry before I could reinstall the unit back into the car! Once you are sure you have filled in all of the holes and the silicon is dry, then reinstall the unit back into the car. Just plug it back in, tighten the two 10mm nuts holding it in place, tighten the wheel well liner, mount the wheel and drop the jack! Don't forget to retorque your lug nuts to 84 foot pounds! If you do this procedure and you still get a "Service Theft Alarm" warning on the SID, then most likely there is another fault with the system. This could be the lift sensor or glass breakage sensor. In order to figure this out, you will have to get someone with Tech II to read the codes.