So I have a 2012 Mazda 3 skyactiv Touring Hatchback model. For whatever reason my hatchback/trunk latch has started opening itself. I know the safety feature is normally hatch/trunk cant be opened if the vehicle isn't in park with all doors unlocked. But today it started opening itself while in park whether the doors are lock/unlock and whether the vehicle is on or off. I tried lubricating the latch mechanism and cycling the open/close a couple times, which didn't solve the issue. My brother who is being trained as a mechanic thanks to the marine corps, suggested to check the wires to the latch mechanism. Haven't gotten to tearing the trim away to check the wiring yet, but figured to make a post incase anyone here has experienced a similar issue and if they figured out how to fix the issue. For now I'm just disconnecting the battery terminals to hopefully prevent power going to the latch mechanism while its parked overnight. I'll be taking trash out soon tonight and will confirm that's a temporary fix to the issue, if it isn't I'll post that it hasn't temporarily worked.

Note: It isn't opening while in reverse, neutral, or drive gears. So at least I shouldn't have to worry about it deciding to open while going uphill and having things fall out into traffic.

 

Update: It is no longer opening while the battery is disconnected. So It seems like its only opening on its own when power is supplied to system or motor is running.

 

Just curious are you Ed ?
Welcome to the forum


The first thing we would have checked is the battery in the remotes.

 

So since I've received my 12 Mazda 3 the ignition key & battery unlock/unlock have been separated due to the plastic wearing down that they no longer stay together. And I was only supplied with one key. So the last 2 years I've been using just the "keyed" section to unlock it and turn the motor on. The auto lock function doesn't work as intended (most likely the driver side auto-lock button is no longer making contact with the board). Also while the trunk latch was opening it self was more than 10 miles away from the factory auto lock/unlock key part of the fob, which doesn't have an "open trunk" function. I'll try changing the battery in the key, incase it is the reason the trunk is opening since I have almost a dozen of the batteries for the key fob. But honestly, its the least of my worries currently since the inspection expires at the end of today (3/31/26) & will be parking it till I can get repairs done to pass inspection willing the inspector overlooks 1 outta 2 cats are missing due to rusted completely through exhaust and replacing it with a stainless system that turned to be a cat delete system. I do have a new cat to be installed just incase. Only noticed the trunk issues while trying to remove the rear shocks to replace & currently the driver side wishbone nut to the lower shock broke free; so now I have to either heat/bend a wrench to get on the nut or ultimately cut open the wishbone to get a socket on & then weld a nut onto the wishbone to get the bolt back in... I'm located in the rust belt and the engineers diffidently didn't account for rusted bolts/nuts on the rear shock system when designing the 2nd gen(s).

M.ade A.fter Z.ero D.esign A.lterations (MAZDA)

 

Not sure what you mean by "Ed?", I am new to the forums as far as posting a thread. But I've learned enough in the last decade doing my own repairs using common knowledge & forums while doing repairs to be able to pass PA PennDOT Safety inspection courses for cars/trucks/trailers under 10k lbs. the first time around while having an associates in both (ASME) 5g/6g structural and 5g/6g (API) pipe welding. But not enough when it comes to potential electrical issues. I'm hoping in the next few years to be able to attend (UTI) for both automotive/diesel repairs as well as potentially nascar pit crew training.

 

Also, note I'm currently on cars 11-13 since getting my drivers license a decade ago & this is the second of two newest cars I own currently. without any professional training.

 

Your user name if the "E" stood for ED?

ed rybarczyk welding techniques - Search Videos


As for my recommendation and you disregarding it.... you asked for help and then decide based on limited diagnostic abilities what any certified Automotive technician would do to rule out a simple battery replacement in the device that can affect more than just unlocking and locking a Mazda. it communicates with the BCM which communicates to the ECU and other stems.

So as you seem to know more than me, I say good luck with your Mazda.

Oh look at my signature below..

 

Wasn't trying to sound rude in my response or insisting that I know more than you. I will be changing the battery in the key fob, just that its a lower priority on the fixes my car needs currently. Also, for whatever reason disconnecting the battery and letting the phantom energy dissipate has seemed to fix the phantom trunk latch issue as of now, all be it is only close to 8 hours the battery has been reconnected.

No the "E" stands for Eric. That is my first name and last name is Ry-bar-czyk. Thanks, seems like im gonna need it. Since I'm currently doing a almost full rear suspension rebuild. Shocks and mounts, sway bar end links, and sway bar bushings.

 

DIY wisdom by disconnecting and reconnecting the battery rarely solves the issues that you have not first found the cause and more often can create other issues. This came about when many did not know how to diagnose a DTC . They assumed that when the battery is disconnected it resets everything. The reality is that it turns off the dash check engine light and the issues remains in the ECU permanent file until resolved. After several engine cycles returns and reactivating the check engine light. There is also always the possibility of damaging other electronic every time you disconnect the battery and reconnect it. Since 1995 more care and thought must be done regarding any service having to do with disconnecting and reconnecting the battery.

Any electrical issues a good Tech writes done a Dignostic tree of what to start testing. The technician will look at the ECU in the 3 main areas and formulate a plane of testing parts for workability and never randomly replacing any guessed suspected part .

There is a reason why better shops. With skilled and experienced individuals charge at least a one hour Dignostic fee to only find the cause of and electrical issue .


Your member user name:
So why in your user name did you choose . (dot) Welding?
The caduceus conflicted with your user name .

I often look at a members profile and user name before responding to and thread they post on.
This way I get an impression about them from the start .

 

Understandable about the checks process of electrical diagnostic which I'm semi familiar about the process just not the how to. I only disconnected the battery since my vehicle isn't able to be parked in a garage and wanted to prevent someone walking by and noticing and deciding to take things inside the vehicle. I have my own code reader, and once my check engine light comes back I'll be checking it for any new codes if it starts the "phantom latch" again. Although I have a feeling since it doesn't have to do with the engine or transmission I'm not going to get a code.

the ".welding" is because I have an associates degree in various welding processes. Wanted to be able to fabricate custom bumpers etc. for vehicles I own, before continuing education into the automotive fields. The pay rates of a welder in my area outweigh my current payrate in another field. So I haven't switched fields yet.