OEM alarm goes off with key (2010 Mazda5)

[Hank3]

Just wanted to confirm that the OEM alarm is supposed to go off in this scenario:

Lock the vehicle with fob; unlock driver's side door with key then the horn starts honking.

Reason I'm asking is because my wife ran into this issue recently where the fob battery was starting to die and was not working consistently. She used the fob to lock the vehicle, but upon coming back, the fob wasn't unlocking the vehicle so she used the key to unlock and get on her way. Vehicle immediately started honking and she wasn't able to stop it from honking until it went through its entire cycle. Not sure why it did this or if it's intended to work this way (for anti-theft purposes?) But if there's a way to disable the honking, that sure would save a lot of embarrassment!

 

[Hank3]

Reviving this thread as the issue of the alarm going off randomly has resurfaced. Upon further research this go around, it appears that a faulty door latch actuator (Front Driver's Door) could be the culprit of what is triggering the alarm for no particular reason. Wife noticed the door lock light in the dash flicker on/off few times during her drive yesterday.

Anyone else experience their MZ5 alarm going off due to the door latch?

 

[5speed5]

My 2007 Mazda5 does the exact same thing. It was quite embarassing at first, until I figured out what was causing it.

I can confirm your research that it is most likely the result of a faulty door latch assembly inside the driver's door. I found this out when I switched out my entire driver's door with one I pulled from a salvage yard in order to get rid of some rust. With the new door installed the problem went away.

Unfortunately, in my case the door lock solenoid in the salvage door was weak, and so I had to swap in the door latch assembly from the original door, and the problem returned. I believe it's just an electrical thing, the latch isn't signalling the alarm module that the key was used to unlock the door.

I get around it by using the key to unlock all the doors at once. I'm not sure if this is the same for your 2010, but on mine if you turn and release the key, it only unlocks the driver's door. However if you turn and hold the key for a few seconds, it unlocks the driver's door, then unlocks all the other doors a second later. This de-activates the OEM alarm and prevents the embarrassing horn honking.