Theft alarm repair on a Saab 9-5.

The theft alarm module on the 9-5 is equipped with its own power source, so it can operate even when the main battery is disconnected. It uses two Sanyo CR17335 3V Lithium batteries, which get recharged while the car is running. However, the batteries lose their capacity with age, and the current eventually drops below a certain value, which triggers a warning in the self-diagnostic system.

If the batteries need replacement, you will start getting the following message on the SID every once in a while:  SERVICE THEFT ALARM 

Saab does not sell replacement batteries, you can only order a complete new module, which is a waste of money. Fortunately, you can find the batteries from an electronics supplier and replace them yourself, if you're handy with a soldering iron. The batteries need to be of the exactly the same type and model as the originals.

Do NOT solder the batteries directly! The direct contact with a soldering iron might heat the battery up too much and cause it to explode. Instead, make sure that the batteries you buy come with external leads attached to them.

Tools:

  • 17 mm socket: wheel bolts;
  • 10 mm socket: alarm module nuts, bumper lip screw;
  • 8 mm socket: wheel lining screws;
  • Torx T25 socket: wheel lining screws;
  • torque wrench;
  • car jack and axle stands;
  • soldering iron;
  • Phillips screwdriver.
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Wheel off

Raise the left front corner of the car and secure it on jack stands. Take the wheel off.
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Lining

Undo the screws on the wheel well lining. There are two Torx screws along the bumper edge, two 8 mm on the inside, and one 10 mm under the lower lip.
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Nuts

Bend the lining away and unbolt the alarm module located right next to the washer fluid tank. There's a 10 mm nut at the top and a screw at the bottom.
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Connector

Unplug the connector from the module. Make sure the car is unlocked at this point, otherwise the alarm will go off if theft protection was active.
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Module

The two halves of the module are held together by six Phillips screws.
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Open

The cover is glued on with rubbery sealant, so you might need a knife or a flat screwdriver to crack it open.
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Board

Detach the board carefully - the batteries are glued to the bottom cover, so you will need to pry them off. Pull the red jumper to cut the power from the circuits.
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Desoldering

Desolder the old batteries. Be careful not to apply too much heat. Do not solder the batteries directly. Instead, detach their leads from the board.
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Batteries

The old pair of batteries (orange) next to a new set (beige). It looks like the batteries are good for about 5 years, accordings to the markings.
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Soldering

Solder the new batteries on, follow the polarity marked on the board. Fit the jumper, assemble the module and re-install in reverse order.

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