04 Toyota Matrix Alarm Bypass

Look behind the driver kick panel, look for a Blue wire with a Yellow stripe. That would be the disarm wire ( if its there). If its there test it with a volt meter. If its the right wire it will show a voltage on it. While watching the meter, unlock the door with the key. If its the factory disarm wire the voltage will drop to 0 momentarily. Then you have a factory alarm.

i work at a toyota dealership and here are your wiring spec that you need to know

for factory security all you need to do is run a ground out when running to the keysence wire it is blue right beside the ignition harness. not likely you will need this. 12v is black, ignition is BLACK/ white, acc is BLACK / YELLOW. your door lock wire are blue yellow for unlock and green for lock. in the kick panel . your parklight wires is green positive trigger in the driver side running board harness you brakes are GREEN/ white and the door pin common is red / YELLOW negative trigger these three are all in the same group of wires. the rear hatch releaseis at the release button on the bash use the blue wire negative pulse. and if you want to connect horn it is at the steering colum near the top it is a green and black wire there are two identical wires so test if you unplug the wire and lock at it is the wire to the side not the middle.

as for tach go to the blue yellow wire right on top of the engine passanger side

and i dont mean to be rude to ranger svo but he is wrong about the test for factory alarm the blue yellow wire is the unlock wore not factory disarm ALL  toyotas use the keysense wire to disarm the factory alarm

hope all this helps