To disable a factory car alarm, first make sure to have the proper tools and materials. Required items are working gloves, a clean cloth, an alarm key and fuse puller, in addition to a spanner and PIN memory reader.
Start the car as normal, but if the alarm sounds when the engine is running, disconnect or stop the engine. Inspect the battery and the wiring, making sure the connections are solid and there are no signs of corrosion. Corrosion and faulty wiring can negatively impact the disabling of the alarm system. If there is corrosion on the battery, wipe it off or use a battery cleaner to remove any caked-on corrosion.
Locate the alarm system box and turn it off with the alarm key by placing it into the slot. Find the fuse box; typically, it is located underneath the steering wheel, but fuse boxes can be located anywhere, so refer to the car manual to find fuse box locations. Locate the alarm fuse, which is identified by the alarm icon on the top. If it cannot easily be found, refer to the fuse box diagram.
Using a fuse puller, remove the alarm fuse, and insert the memory reader into the slot. This allows the vehicle to retain the existing data. Disconnect the battery's negative charge, and keep the connection separate for at least three minutes before reconnecting the charge.