Anti theft alarm keeps going off

[Q70sGuy]

Looking for some ideas of others who have experienced this. It’s winter and my car has started randomly having the antitheft alarm go off. Haven’t changed anything in my car and no BCM codes nor has the dealer been able to « see » what triggered the alarm. It’s very intermittent; It will usually go off and then keep going off every half hour until I just leave the car unlocked. I tried disconnecting the hood latch to see if that was the issue - it actually stopped going off for a few days but it’s going off again.

It’s anywhere between -10 and -20 Celsius here, so I won’t be doing any in depth diagnostics until springtime. Battery tested as good as well.

Ideas? Thanks

Thanks

[VStar650CL]

The culprit is almost always the lock cylinder switch. The switch is part of the lock and latch assembly, not the cylinder (there's a linkage rod connecting the cylinder to the lock/latch). Usually the false alarms are from bad or wet switch contacts sending phantom signals to the BCM.

[Q70sGuy]

Thanks for the reply! I was reading the service manual and I thought it was that little door switch near the latch which was the only thing that triggers it, I’ll have to read more carefully now.

Is there a way to test this or would it be easily noticeable if I pulled it out and looked at it or did some testing with a meter?

I am assuming it’s the drivers side which is most common - and the fix is replacing the complete door latch assembly?

[Q70sGuy]

Additional info: read through the service manual again and it doesn’t really say what it uses to detect an « open door » situation.

Page SEC-17 explains that it goes from ARMED to ALARM when it detects door, hood, or truck « open » but how exactly it decides that I’m not sure. I was convinced it was just the door switch which makes that determination.

Thoughts?

[VStar650CL]

The BCM monitors the door, trunk, and hood switches, and only the hood switches are anything special (double throw). The rest of them are just SPST grounding switches with pullup resistors inside the BCM. Those aren't usually the underlying problem. On an I-key car it's usually the lock/unlock switch showing unlock activity when there's no fob present. That makes the BCM think there's an illicit entry in progress. You can see the switch details on DLK-117 and the diagram on DLK-51:
https://www.nicoclub.com/service-manual ... %2Fdlk.pdf

[Q70sGuy]

Is there any way to test the switch given it’s pretty intermittent? In most cases you’ve seen it on the driver side I am guessing?

[VStar650CL]

Only if you have a scanner which can read the inputs from the BCM, or you can rig a voltmeter with min/max capture on the two switch data lines. There's no particularly easy way.

Yes, it's usually the driver's side, but that's because most cars only have a driver's side cylinder and in any case the driver's side gets the most work. If the car has a passenger side cylinder, you need to check the FSM to see if it has a switch. If so, that can cause it too.

[Q70sGuy]

that’s funny I completely forgot there aren’t any passenger side locks anymore. Thanks for the help! I’ll see what I can find out maybe I’ll give it a visual inspection to start..

[reggiebrown40]

The BCM monitors the door, trunk, and hood switches, and only the hood switches are anything special (double throw). The rest of them are just SPST grounding switches with pullup resistors inside the BCM. Those aren't usually the underlying problem. On an I-key car it's usually the lock/unlock switch showing unlock activity when there's no fob present. That makes the BCM think there's an illicit entry in progress. You can see the switch details on DLK-117 and the diagram on DLK-51:
https://www.nicoclub.com/service-manual ... %2Fdlk.pdf

Just curious why you don't think those door switches aren't the problem? The door jamb switch is where I wired my alarm to trigger the alarm. If the switch itself goes to 0v it will trigger the interior lamp and the alarm will go off. Something as simple as the screw that attaches the switch to the jamb being loose can cause this. This is where I would check, OP. Check all doors.

[VStar650CL]

He didn't say it was an aftermarket alarm.

I've been talking about the factory one. Aftermarket ones often have tip switches and all kinds of other crap which the factory doesn't employ. So if it's aftermarket, all bets are off unless he can link me to the documentation for it.

[reggiebrown40]

He didn't say it was an aftermarket alarm.

I've been talking about the factory one. Aftermarket ones often have tip switches and all kinds of other crap which the factory doesn't employ. So if it's aftermarket, all bets are off unless he can link me to the documentation for it.

I'm using the FACTORY alarm and triggering it with a sensor that triggers at the door jamb. Nothing aftermarket about it. You still didn't mention why it couldn't be the jamb....

To the original poster: I would first check the wiring at the switches at the door jamb. Those things are held in with a grounding screw. If the screw gets loose, it grounds to 0 volts and triggers the FACTORY alarm.

[VStar650CL]

I'm using the FACTORY alarm and triggering it with a sensor that triggers at the door jamb. Nothing aftermarket about it. You still didn't mention why it couldn't be the jamb....

I didn't say it couldn't be, I just said it isn't the most likely culprit. Unless the rubber seals are shot or the car is a rustbucket, the door jamb switches simply don't fail very often. The lock assembly switches live in a much more demanding environment and fail frequently.

[Q70sGuy]

Yes it’s the oem panic/antitheft as far as I know. Not aware of anything aftermarket in this car besides a remote started(which I suspected could be messing with the BCM too)

I don’t think the door switch is bad simply because I have never seen the cluster warning come on while the door was closed. I also tried to trigger the alarm myself by pushing and pulling on the door s but nothing made it trip.

Been a few days now - no more false alarms - so this just makes it even harder to track. I suspect something like vstar said - humidity is entering somewhere and hot/cold cycles are messing with that

[Ilya]

I trust VStar on here explicitly but I have this issue and it seems to be related to how healthy the battery is (hence why I disabled the idiotic ECM controlled alternator bug) but also how healthy the battery for the remotes are. Like you, I only have a Fortin remote starter and everything else is basically stock.

I had MAJOR issues with this before I disabled the 'feature' and have since kept my battery on a tender and haven't had many episodes over the years.

[VStar650CL]

I trust VStar on here explicitly but I have this issue and it seems to be related to how healthy the battery is (hence why I disabled the idiotic ECM controlled alternator bug) but also how healthy the battery for the remotes are. Like you, I only have a Fortin remote starter and everything else is basically stock.

I had MAJOR issues with this before I disabled the 'feature' and have since kept my battery on a tender and haven't had many episodes over the years.

You're quite right, Ilya, an unhealthy battery or a chronic draw dragging the battery down can definitely cause the BCM to lose its mind.

[Q70sGuy]

Thanks folks, Ilya I asked you about it on your old post on the Facebook group and so I had the battery tested at the dealer and it was good. No false alarms yet either since I wrote this post.

Vstar I saw in the service manual that it’s possible to just disable the alarm system using consult. Am I reading that right? If so and if it goes off again I think I’ll just ask the dealer to disable the system as I don’t care for it anyway

[VStar650CL]

Some models are configurable, some aren't. Happily, ASIST says yours is. It's under BCM -> Theft Alarm -> Work Support -> Security Alarm Set. One caveat, sometimes those "work support" settings are stored in RAM and not flash, so they default to the factory setting if your battery is disconnected or goes dead. They don't specify that in the FSM, so I can't tell you for sure if that applies to your Q.

[Ilya]

I jinxed myself chiming in here. Had two false alarms the other day lol. I ended up unplugging my GROM Audio VLine system in the glovebox (as that usually stays on for 15 minutes or something after the car is driven) and noticed my battery tender was actively juicing the car - hasn't happened since. The tender is showing as charged/maintaining now as well.

[Q70sGuy]

No false alarms since my post and I haven’t done anything … guess I’ll just live with it lol