Thursday, July 7, 2011

Security alarm not letting the lexus ls- 400 to start?

Ok, take it to the installers, and tell him
to locate the GREEN wire coming into the
car from the drivers side door, and either use
the factory (-) disarm wire from your system,
(if it exsists)
or, to add a relay (negative) to the (-) door
unlock wire on your alarm, then to the GREEN wire,
in the wire pack coming in from the drivers door,
to disarm the factory system at the same time the
alarm system is unlocking the door
(see this diagram at under
disarming factory alarms)
or, permanantly ground the green wire
to the chassis of the vehicle,
to disable the factory system for good.
There is a part called a key detection switch in each front door, this has fallen off, come loose or is just bad, it is located on the back of the lock cylinder that the key goes into and so when you turn the key to lock or unlock in the door it tells the security system to disarm or arm. So if you use the key on the driver door and this is not sending signal the security sees the door open and no unlock signal sent so it sees this as a break in.
you will need to remove the interior door panel to see the inside of the door so you can access this detection switch on the back side of the driver door handle where the key lock cylinder bolts in.
There is no way to disable factory security, the system is integrated. Pretty much if the switch is in place and connected to the back side of the key cylinder then it is bad, usually what I see on these is either the switch is worn out and bad or the unit was damaged/broken when some one tried to "jimmy" the lock open when they locked the keys in so they pulled on the detection switch wires when sticking a jimmy rod into the door.
Try this to stop the alarm from coming.Lock and unlock the car from the passenger side door.

If that is not helping then other procedure to reset is as follows:---
Disconnect the battery both terminals . Then insert the key and turn the ignition to where the radio would work then reconnect the battery and see if it starts.The battery needs to be disconnected for approx 10 minutes.-------