2013 CX-9 Rear automatic door locks sometimes working

Hey Folks,

I have a 2013, CX-9 Touring. Both automatic rear door locks have started acting up recently. I can't be sure but I feel like they started malfunctioning simultaneously. The car is in superb condition at 68,000 miles.

In particular they don't want to lock when using the key fob or using the 'lock all doors button' on the driver's door. They always unlock using the key fob and the button on the driver's door.

In contrast when I put the car in 'drive' the rear doors lock perfectly! Likewise the unlock perfectly when the car is put in 'park'. I've only been monitoring this behavior for the past 3 days but it seems to be consistent so far.

So my questions are:

Has anyone experienced this same thing? Any solutions (lubrication, etc.)?

I feel like the obvious answer is somewhere with lock actuators however wouldn't both locks would be malfunctioning more consistently?

I purchased this as a certified pre-owned Mazda and am wondering if I have any warranty/recourse if I need an extensive repair.

What type of warranty did you get with the cpo vehicle. Usually you get a short warranty along with a longer powertrain warranty up to 100k. See what your paperwork says about coverage and term.

Hey Folks,

The plot thickens on this intermittent door lock issue. I'm still searching for an answer or at least some leads.

1) My car battery was tested shortly after the original post. It tested faulty. It was the factory battery and was just about 4 years old. I replaced the battery but the intermittent lock issue still happened.

2) I live in Atlanta and the summer months are brutally hot. The heat and humidity absolutely makes the problem worse. We recently had a cool snap where the highs barely reached the low 80s with lower humidity. All the locks perform perfectly at cooler temps with the key fob and with the switches in the car. Why is the heat making this happen? If you search online you'll see a lot of people having the same heat related issues on many different makes and models of cars. However, I've yet to find a solution.

Any other ideas or possibilities?

gretschdrum said:

Hey Folks,

The plot thickens on this intermittent door lock issue. I'm still searching for an answer or at least some leads.

1) My car battery was tested shortly after the original post. It tested faulty. It was the factory battery and was just about 4 years old. I replaced the battery but the intermittent lock issue still happened.

2) I live in Atlanta and the summer months are brutally hot. The heat and humidity absolutely makes the problem worse. We recently had a cool snap where the highs barely reached the low 80s with lower humidity. All the locks perform perfectly at cooler temps with the key fob and with the switches in the car. Why is the heat making this happen? If you search online you'll see a lot of people having the same heat related issues on many different makes and models of cars. However, I've yet to find a solution.

Any other ideas or possibilities?

Click to expand...

One possibility to look into is the BCM (Body Control Module) it is located in the windshield pillar by the driver side, do you have a sunroof ? sometimes that gets clogged and when it rains the water trickles down and shorts out the BCM which controls the automatic locks, it's worth investigating, seems like your BCM is sensitive to warm weather for some reason, maybe when it's warm some wires are expanding and shorting out and when it's cool it contracts and works fine.

http://www.mazdas247.com/forum/showthread.php?123729823-CX-9-Body-Control-Module-%28BCM%29-failure

astriuminc said:

One possibility to look into is the BCM (Body Control Module) it is located in the windshield pillar by the driver side, do you have a sunroof ? sometimes that gets clogged and when it rains the water trickles down and shorts out the BCM which controls the automatic locks, it's worth investigating, seems like your BCM is sensitive to warm weather for some reason, maybe when it's warm some wires are expanding and shorting out and when it's cool it contracts and works fine.

http://www.mazdas247.com/forum/showthread.php?123729823-CX-9-Body-Control-Module-%28BCM%29-failure

Click to expand...

That, my friend, is a good call. Let me say this though. I do not have a sunroof and haven't had any water damage. However, after reading up via your recommendation I have to say the BCM is a good possibility. The humidity in Atlanta is deplorable...absolute steam room-ish from May until October. So the overall stickiness of the typical weather down here may have something to do with it.

I wonder if it's possible/prudent to put a small packet of desiccant in the BCM case? Thoughts?

If anyone else has had a BCM repaired/replaced please let me know your results.

gretschdrum said:

That, my friend, is a good call. Let me say this though. I do not have a sunroof and haven't had any water damage. However, after reading up via your recommendation I have to say the BCM is a good possibility. The humidity in Atlanta is deplorable...absolute steam room-ish from May until October. So the overall stickiness of the typical weather down here may have something to do with it.

I wonder if it's possible/prudent to put a small packet of desiccant in the BCM case? Thoughts?

If anyone else has had a BCM repaired/replaced please let me know your results.

Click to expand...

UPDATE: It's cooled down a good bit in Atlanta. More importantly the humidity is significantly lower. Guess what? The door locks are working perfectly. I didn't clean or repair anything. They just started working again.

So, is this sounding like the BCM? Any other ideas?

I suppose if we have another very hot, humid day I could take note...either that or wait til next summer.


2017 UPDATE: So, I've been dragging my feet repairing the locks....sue me. But, once again we've hit autumn and the temps and subsequently the humidity have dropped precipitously. The locks work better but not perfect. The rear door locks in particular were completely dead from April until mid October but they have sprung to life and work well on colder, drier days.

So, I'm throwing this out one last time before buying a BCM and seeing if that works (FYI, no OBD codes show up). Anyone have any new ideas or possible solutions?

Bump....please check the most recent update directly above this post.

I welcome any and all advice for the electrical/lock issue.