Hello..

I just recently took delivery of an '05 TL a few weeks ago and i i realized my factory alarm doesn't engage when i lock the doors. When i open the doors using the remote, the side lights blink twice, but when i lock the doors, the doors do lock, but the light that is supposed to blink does not blink and my red "security" light doesn't go on. i tried to open and shut the doors numerous times, and sometimes the alarm engages and sometimes not.

if anyone knows any fixes, it would be greatly appreciated.. thanks!!

 

There are “sensors” in every door, the hood, the trunk, even in the audio system. The alarm system only arms when every sensor is grounded. For example: if a door is closed, a sensor in the doorsill is connected to body ground. Once the door is opened, the connection to the body ground is lost and the switch is left open. If the system is armed and then any of these switches is opened, the alarm is set off. If any one of these sensors gets corroded or otherwise looses its electrical conductivity (or, if any of the doors/trunk are left open) the alarm will fail to arm, and thus our problem.

About 2 days ago, I started having the same problem you did. The car will lock fine but the lights do not flash nor does the red armed status light. Whatever the bad connection is, it's intermittent. My alarm has gone off twice just sitting in the driveway. Sometimes it arms fine, sometimes not at all. Seems to be related to the humidity.

Anyways, troubleshooting the failure is quite easy. The signal from the sensors on the left half of the car, the trunk and hood are received by the drivers multiplex unit. The signal from the sensors on the right side and the audio unit are sent to the passengers multiplex unit. Figuring out which sensor is bad is a matter of removing the multiplexer and checking the voltage at a given pin when various conditions are in place. I would imagine it would take no longer than 20 minutes to do both multiplexers. I plan to have some time either this evening or this weekend. With any luck it's just a loose wire somewhere.

I can post a how-to if you'd like. It takes little more than basic electrical know-how. Most importantly, don't waste your time/money with the dealer.

 

Thanks!!

I also noticed my alarm just going "on" in the middle of my driveway too. Could you please post a how-to on how to diagnose the problem. I took it to the dealer twice before, but they couldn't look at it b/c it seemed to work when i took it there. Just like you said... it was a waste of time.

Thanks soo much!!

 

I found the my rear passenger lock actuator was bad. It would only lock/unlock about 1/2 the time I was commanding it to. The fix was to remove the actuator and give it a good cleaning/greasing and reinstall. Good as new. Check to see if all your locks are opening and closing when you press the button on the key fob. Try it in hot weather, as mine functioned normally when the temp was below 90 or so.

 

the only time i experienced this situation was when the temp was 95 degrees and above. do u have any diagrams on what i should look for or pics? i have no idea where to look. thanks!!

 

Do youself a big favor and purchase the Helms manual for your car. The best $60 youll ever spend on your car:

http://www.helminc.com/helm/product2...QD59HKJ8W8065F

 

thanks soo much stein. i'm gonna order it right now