Have a 2021 CX5 GX. I have the door lock system setup so that when I use the unlock button on the fob, all doors (including the rear hatch), unlock. On cool temperature mornings the lock on the rear hatch sometimes will not unlock (all other doors unlock). The problem is intermittent. All the passenger doors always work but the rear hatch lock sometimes won't unlock. I hit unlock several times on the fob and it sometimes unlocks. If it doesn't, I use the unlock button on the driver's door. Sometimes that works. There are times it just refuses to unlock and I'll drive the car and then it usually works. When it refuses to unlock, I don't hear a mechanical noise at the hatch lock. Am I correct to assume that the rear body module sends a signal to each lock (separately) to actuate the lock mechanism? Is that lock a mechanical item, ie: plunger or switch which moves to unlock/lock? In my opinion it is the lock/latch assembly that is at fault. I've had the car back to the dealer twice now. They have "reset" the lock settings in the setup, and scanned for codes (there were none). I will be taking it back to the dealer next week. The service manger seems to think that a microswitch in one of the other doors is affecting the system causing the hatch lock to fail. Are there microswitches in the doors? I don't buy that story. I think the lock/latch assembly should be replaced. Any information would be appreciated. Thanks.

 

There are a whole host of issues that can cause your problem and most of them are electrical.
On my 2020 the hatch module was recalled and new one replaced though I never had an issue.
I would first make sure the latch is properly aligned and lubed correctly, if that is fine, I'd have the module checked.

 

Is there somewhere i can see a wiring diagram of the sytem to confirm what is in the system?

 

I'm not aware of any free ones.
There are some websites you can purchase a PDF download form, but I don't how good they are or if they are "safe" to download.

 

Took the car to the dealer. Of course they couldn't get it to fault. No faults code found. Mazda Canada told them to change both of the front door latches. Tested servicable. So far no failure but the weather has been pretty warm and this would only fail on the first try on a cooler morning. Fingers crossed.

 

Analysis of the issue makes sense. The rear hatch lock assembly likely includes a solenoid or actuator mechanism that should receive signals from the body control module (BCM) to lock and unlock in sync with the other doors. It’s possible there’s a fault within the hatch’s lock actuator itself, especially given the lack of mechanical noise when it fails to unlock.