The midsize MDX is one of Acura’s best selling models and is known for its excellent reliability, third row seats and handling.
But like other cars, it can have door and keyless locking issues from time to time.
In this article, we’ll take a look at some of the most common locking problems owners have encountered with their Acura MDX and look at possible solutions.
Table of Contents
1. Acura MDX Locks Not Working
If your Acura MDX’s door locks are not working, you probably have a faulty door lock actuator.
The Acura MDX uses Honda door lock actuators which are a common weak point in a lot of Honda and Acura models.
The driver’s door lock actuator is usually the first that goes because it’s the most used. It’s not uncommon for these to break after 5 years of regular use. Multiple actuators can also break at roughly the same time.
Here’s how one MDX owner described their experience:
“Just started happening to my 2014 MDX. All doors unlock with the fob except driver and same when I hit the internal unlock button. I actually had to get in through the passenger side and manually unlock. Dealer had to replace the door lock actuator.”
Before you change the actuator, check the fuses and relays first and replace them if necessary.
A broken door lock actuator usually also makes a buzzing or grinding sound before it completely stops working.
New OEM door lock actuators are around $50 to $$60 while replacement units are around $25.
You’ll have to take off your door panel to replace the old one, which usually only requires a screwdriver.
Other common causes you can check out include:
- Driver door switch
- Door mechanism and linkages
- Wiring and wiring harness problems
- Key fob issues
- Worn out key lock cylinder or tumbler
- Body Control Module (BCM)
- Weak 12-volt battery
Before buying any new parts, troubleshoot the problem first and try to isolate the issue.
2. Acura MDX Unlocking Itself
Faulty door lock actuators usually have trouble keeping the door locked.
It’s also possible that you’re inadvertently hitting the unlock button on the key fob while it’s in your pockets or bag.
A faulty door lock actuator can unlock the door on its own as soon as you hit the lock button, but it can also unlock slowly over a few seconds.
If you drive with one of the doors unlocked, the BCM (Body Control Module) will keep relocking and cycle the door locks in stop and go traffic.
Here’s how one MDX owner described their issues on the MDXERS.org forum:
“My 2015 Tech started to have this keyless entry problem and more. It’s trying to lock when the vehicle start to roll, but as soon as it locked it unlock by itself again instantly, even if I pressed lock on the master window switch while the car moving it unlock itself again instantly.”
Replacing the door lock actuators should make the doors stay locked and keep your car safe when parked.
If replacing the door locks doesn’t fix the issue, you might have a wiring or BCM (Body Control Module) problem.
The MDX will also automatically unlock the doors in certain conditions such as when you turn off the engine or put the vehicle in Park. But you can change these, and also set the power locks to unlock just the driver’s door or all the doors, in the vehicle settings.
3. Acura MDX Keeps Locking Itself
The Acura MDX doors will automatically lock its doors when you go over a certain speed or shift out of park.
If you have faulty door actuators that keep unlocking on their own, you’ll constantly hear door locking sounds in stop-and-go traffic.
Here is how one MDX owner described their experience:
“The door lock on my ‘09 MDX kept locking itself a few times throughout the duration of the drive whenever I did a complete stop, then go.”
It will also automatically lock itself if you unlock using the remote but don’t open any doors within 30 seconds. Opening the tailgate doesn’t stop the auto locking.
This is a security measure to prevent break-ins if you accidentally push the unlock button on the key fob.
Although the doors shouldn’t lock themselves if the engine is running or when the key fob is inside the car, some owners have had their cars lock on their own on certain occasions.
“2001 MDX. One other autolock problem. Wife started out of drive; forgot purse; left engine on (keys inside of course) went into house, returned to find car locked.”
“That happened to us one time too. Acura said it was a glitch — a one time thing. That was on my ’03 model. We haven’t had any issues on our ’04 model.”
Since the problem is quite rare, it’s hard to pinpoint what causes the doors to lock on their own.
It’s possible the key fob battery is starting to get weak and the car had trouble seeing the key fob — causing it to automatically lock. In older cars, it might be an issue with the switch in the ignition.
You can unlock the car using your second key fob or physical key. However, if you don’t have access to them, you’ll have to call a locksmith.
If it persists or if you can easily recreate the problem, your dealership or mechanic should be able to diagnose the issue better.
Possible causes of the auto locking problem include:
- Faulty door locks
- Wiring problems
- Electrical issues
- Stuck door mechanism
- Key fob problem
4. Acura MDX Not Locking With Key Fob
Some MDX owners have had issues locking their car using the key fob remote.
Here’s how one owner described their issue:
“On my 07 MDX, I can still unlock the car totally fine. But I cannot lock the car remotely with my keys. I can also press the lock button on the door and after I close the door, all doors will be locked.”
You won’t be able to lock the doors using the key fob if the hood, tailgate or one of the doors is still open, so make sure they’re all properly closed.
If all the doors are closed and you still can’t lock the car using the key fob, there might be an issue with the door jamb switches, hood latch or tailgate switch.
A broken switch will make the car think that one of the doors is still open.
If you can lock your MDX using the spare key fob, then you might have an issue with the lock button on the remote. You can try opening up the key fob and cleaning the circuit board to get the lock button to work again.
Other things you can try to fix the locking problem include replacing the key fob battery and reprogramming the key fob.
If only one of the doors isn’t locking with the key fob, it’s likely just an issue with the lock actuator or the locking mechanism.
5. Acura MDX Not Unlocking With Key Fob
Some MDX owners have had trouble unlocking their doors using the key fob.
Here’s how one owner described their issue:
“In the past few days I’ve been having problems unlocking my truck with the remote key and the actual key won’t work to unlock the car manually. I have to keep pressing the lock and unlock for about 5 min everyday for it to start working.”
Those with smart keyless entry systems have also had issues getting their car to recognize the key fob and automatically unlock the doors when grabbing the exterior handle.
“I have a 2014 mdx with keyless entry. The driver 1 fob works good but driver 2 most of the time Don t open the door when approaching. I change battery with no success.”
“Mine will work however you have to be basically touching the car to unlock or lock doors. We replaced the battery twice and still the same.”
In a lot of cases, replacing the key fob batteries with new quality name brand batteries usually fixes a lot of keyless entry and key fob glitches.
However, many MDX owners have found the the only solution to their unlocking and range problems is to replace the key fob altogether.
If you’re unable to unlock the doors using the button on the key fob, you can also try opening up the fob and cleaning out the insides using some electronics cleaner. This can remove any debris or corrosion that might be affecting the fob’s functionality.
If only one of the doors doesn’t unlock, then you might have a bad door lock actuator or a wiring issue.
If you just need to get into the car, you can also just use the hidden emergency key inside the fob to unlock the driver’s door. This lets you open the car even if the 12-volt battery dies.
6. Acura MDX Door Not Locking
If only one of the doors on your Acura MDX is not locking, then it’s probably got a bad door lock actuator or something’s wrong with the linkages inside the door.
Here’s how one MDX owner described their experience:
“We have a 2005 MDX we bought used a year and a half ago. Recently, the driver’s door unlock function quit working both with the remotes and the switch inside of the vehicle. I bought a new actuator. Unfortunately, this did not solve the problem — the door lock is doing the exact same thing.”
It could also be caused by a wiring or electrical problem so you’ll want to check the wiring harness for loose connections and grounding issues.
If you’ve already replaced the actuators and checked for wiring problems, the next step would be to take the car to an experienced mechanic who has the tools to properly troubleshoot the issues.
7. Acura MDX Tailgate Not Locking
Many Acura MDX owners have issues with their tailgate not locking at all using the key fob.
A faulty actuator in the tailgate might cause this problem, but another common cause is the wiring harness in the tailgate which tends to break in the MDX due to repeated use.
Here is how a few owners describe their issues:
“When locking all the doors, the tailgate lock doesn’t lock. It’s always open.”
“I had the same problem with the tailgate not locking via the remote. (All other doors locking). I assumed the actuator in the tailgate had died. For others with the same issue make sure you check the wiring in the rubber boot going from the body to the tailgate. When I pulled back the boot there was the problem, a broken wire.”
Before getting a new actuator, check the wiring harness that goes into the tailgate. If you see any broken wires inside, you can repair them individually or just replace the entire harness.
8. Acura MDX Tailgate Not Unlocking
The second generation Acura MDX tends to have issues unlocking the trunk button using the driver’s door switches.
Here’s how some owners described the problem:
“I have a 09 MDX with tech package. My power tailgate button does not open my tailgate. The remote does open tailgate no problem.”
“My 2008 MDX has a weird problem. The driver side power door lock doesn’t work. If we have to open the tailgate, first unlock all the doors using the passenger side door lock and then open the tailgate using the tailgate opener.”
Although it seems like the problem could be a defective driver’s door lock switch panel, it’s actually the driver’s door wiring harness that usually causes these door and tailgate unlocking problems.
If the tailgate has trouble opening, there might be an issue with the latch mechanism, the external tailgate button or the release handle.
Here’s how a few owners described their problems:
“2001 MDX Touring 175K miles. Tailgate this morning refused to open. The pull lever is sticky but I can lube that. It seems as if the pull lever is no longer connected to the releasing mechanism.”
“I have a 2018 MDX. When I go to the tailgate and press the open/close button, it takes at least three presses for the tailgate to finally open.”
If you just want to open up the tailgate as soon as possible, there should be an emergency release lever under the tailgate’s interior trim.
In older MDXs, either the handle or the locking mechanism inside the tailgate can get stuck. You can try spraying a liberal amount of WD-40 or lubricant to get these parts to work smoothly again.
For the third gen MDX, there’s a TSB (Technical Service Bulletin) that recommends replacing the outer tailgate button because it stops working in colder weather.
It’s also worth noting that the tailgate will only open if all of the doors are unlocked. This means that a broken door lock actuator can also cause the tailgate to not work properly.
9. Acura MDX Not Beeping When Locked
Normally, the Acura MDX will beep at you if you press the lock button on the key fob twice. This means that the security system is armed.
However, if one of the door lock actuators isn’t working and one of the doors is unlocked, you won’t hear the confirmation beep because the security system is not yet armed.
Here’s how one owner described their experience on MDXERS.org
“Just started yesterday on my 05. I didn’t hear the confirm beep, then I find the rear passenger side door doesn’t lock or unlock, either remotely or with the chrome lock/unlock switch.”
Other issues that prevent the doors from locking using the key fob, such as an open door, a broken door switch or a faulty hood latch, will also affect the confirmation beep.
The ‘Keyless Access Beep’ could also be disabled in the vehicle settings. You can usually find the setting in the ‘Door Setup’ menu.