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My car alarm (2007 Mercury Mariner) has been going off uncontrollably at all hours and my neighbors are furious. I cannot afford to take it to the dealer, who wants hundreds of dollars to even look at it. I don't have the time (or money) to try to replace all the sensors. I don't want the car alarm at all. If there was a way to just remove it, I would do it in a heartbeat.

Can the OBD port be used to disable the car alarm? Can it be used to at least see which sensors are misfiring?

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  • I'd be surprised if there wasn't a fuse that could disable the system. I'd say on some cars the ODB Port could be used, but it would not be a generic ODB protocol. It would be a proprietary protocol that only a special scan tool could use.
    – JPhi1618
    Oct 27, 2017 at 17:44
  • So, looks like I was wrong. The "BCM", Body Control Module, has constant power and can't be "disabled" with a fuse. It can be diagnosed with a Ford scan tool through the ODB port, but not sure if it can be disabled. I did read some reports of problems with your particular BCM.
    – JPhi1618
    Oct 27, 2017 at 18:30
  • @JPhi1618, thanks so much for the insight—are there any DIY ways to interface with the BCM? Would replacing it be any help?
    – T3db0t
    Oct 27, 2017 at 19:28
  • What I saw seemed to indicate the issue could also be an intermittent door switch problem, so you could replace it, but I think it has to be coded for your car, so that might not be DIY, and might not fix the issue if everything else isn't ruled out first. Maybe disconnect the horn, or wire a switch to the horn so you can turn it on and off when you leave the car?
    – JPhi1618
    Oct 27, 2017 at 19:36
  • @JPhi1618 yeah; I do have a battery disconnect hooked up right now, but I guess there's just not a really good solution without shelling out a ton of money. :(
    – T3db0t
    Oct 27, 2017 at 19:46

1 Answer 1

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Maybe someones google skills are better than mine. I wasn't able to find custom firmware to flash the Smart Junction Box and disable the perimeter alarm. You would still need a J2534 device to accomplish this.

If you have access to the Ford IDS or an aftermarket EOBD2 scantool you can go into the body data to find the malfunctioning switch.

These two connector pinouts show the location of the door, hood and lift gate ajar signal terminals. IIRC each switch is grounded when the switch is closed. You can test this by manually closing the door latch. Also consider the wiring to the door's. They tend to see a lot of flexing and should be considered as well as the switches.

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If you want a work around than you could ground the failing switch at the SJB. Effectively the SJB would never see the switch open.

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