05 STS alarm going off/hood ajar/theft detected

Wiring, DIY, lighting, etc.
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kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

05 STS alarm going off/hood ajar/theft detected

Post by kevm14 »

This is the first time I've actually caught the alarm going off though it may have happened before when I couldn't hear or see the car for all I know.

What I HAVE been getting for easily over a year is intermittent "HOOD AJAR" indications, often combined with "THEFT ATTEMPTED" or some similar display on my dash. Looked into it...common issue. I think it is basically corrosion from water or something and electrically it sort of just eventually fails (the switch part in the latch). I did power wash the engine bay this weekend (including washing with soap, after I washed the car itself) and I am sure the latch got pretty wet though I tried not to spray directly at it...

Here is a GM bulletin on it, dated, seemingly impossibly, August 26, 2005. The number has also been superseded. Original was 15785120. New number is 25778967. Not sure when the latch was redesigned or what happened there - presumably due to this issue?
https://www.justanswer.com/cadillac/4s1 ... rning.html

New one is almost $170 with shipping. That kind of sucks.

Mitigation options include:
- Blast a bunch of WD-40 or perhaps contact cleaner in there and see if that changes anything
- Disconnect plug and attempt to jumper out the switch, or do so with a resistor if it is not just a open/closed switch. From an alarm standpoint, the idea of someone prying open the hood with a crowbar seems like....I have a problem that the alarm is not going to fix anyway. Unless I'm missing something. Well, technically if I parked with the windows down, and someone reached in to release the hood (i.e. to disconnect the battery so the alarm DOESN'T go off), it would honk and flash at that point (at least until they did actually disconnect the battery, which would take all of 10 seconds). Otherwise I kind of don't see the real point to a hood intrusion alarm. I think most factory alarms have hood switches so this is nothing new. My parents' old 1990 Lincoln Continental did though I don't think it was integrated into the hood latch.

Anyway it went off last night while I was in the house and also did something funny on me this morning after I parked (it went off immediately after I locked it, indicating that there was probably a continuous intermittent short internally which would only matter after arming). It is SUPER humid. I may attempt one last douche with some spray before I give in. I can't even see where the plug is otherwise I'd unplug and spray that, too. I am not sure I want to wait until it goes off in more inconvenient circumstances. I also would not like to receive an all hands e-mail at work that a stupid Cadillac is honking and flashing in the parking lot...or have it go off in the middle of the night which I may or may not hear...

Oh, the other flaky thing the alarm does is it has gone off when I open the trunk. Now the trunk popper works only when the key is in proximity. So the only way the popper should actuate is if it validates my fob. Yet, that has set the alarm off on more than one occasion, including in the parking garage at the airport when we came home this weekend. Annoying. Not sure if related to the hood somehow. Or maybe a trunk latch issue though I don't know if that is common at all. I do think the flakey hood latch probably causes the alarm not to arm properly and maybe that has something to do with the false alarm when opening the trunk. It is very infrequent.

I would bet that I could probably arm it and bounce the car lightly and get it to go off if there is really water in the switch/sensor.
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: 05 STS alarm going off/hood ajar/theft detected

Post by kevm14 »

It's time to order. Alarm just went off. Reset, locked. Went off again. Went outside, opened and closed hood. Locked doors. Alarm went off again. So....I guess it's failed. Doors just unlocked at this time....

$169.66 shipped from GM Parts Giant.

This will give me a chance to tweak hood closure alignment. It needs to be adjusted a little higher (closes a bit too far).
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: 05 STS alarm going off/hood ajar/theft detected

Post by kevm14 »

Installed. That was easy. Like 30 mins total plus a little extra for tweaking hood closure alignment/height.

To give a little access room I removed the upper radiator cover which is just two plastic push rivets. I also removed the 4 that secure the upper grill/bumper so I could pull the grill back a bit. I marked the old latch on the upper corners with a sharpie since it is highly adjustable. Three 10mm bolts and it was out. Remove hood release cable. Unplug the switch harness. That's it.

As I mentioned before, I raised the setting a bit and also unscrewed the rubber stops on either side to give the hood a higher closure position. The body lines are nice and even now. Therapeutic for my OCD I guess.

Expensive part but easy to replace. Ian wanted me to test it so I did. I rolled down the driver's window, closed the door, locked the car and waited like 20 seconds. Then I reached in and pulled the hood release lever to simulate someone trying to break into the hood (to disconnect the battery presumably). As it is supposed to, the alarm went off. Of course the reason I replaced it was because of false alarms which I can't really test other than not having them anymore and having the DIC say "THEFT ATTEMPTED" or something when I start the car occasionally (or sometimes it would say the hood was open). So all of that should stop. Yay.
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The switch actually looks like a different design. Different shape. Probably a good thing.
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This gap is my fault when I reinstalled the headlight 500 times. By the way, STILL DRY!
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kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: 05 STS alarm going off/hood ajar/theft detected

Post by kevm14 »

Not one false alarm since installing the new hood latch.
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