2015 CX-5 Key Fob on occasion will not start car. Dealer is at a loss. Happened to anyone else?

Partially Solved: For some reason after the car sits for an extended period of time the brake pedal becomes very difficult to push thus activating the switch. If one pushes on the pedal very hard it will activate the switch. When this happens it is like pushing on the brake pedal to stop when the car engine quits and the vacuum assist is off.We owned a 2014 CX 5 and this never happened. Dealer says it is normal.

I had the same fault with my cx5 2015 model I replaced the battery in the remote with a cheap and nasty one but still had the same fault I could open the doors with the remote but it couldn't start the car. so I went out and got a Lithium battery, it has been working fine for 4months now with out a problem. Give it a go it could be a quick and easy fix. As for the brake peddle going hard it sounds like a vacuum leak in the booster or the check valve is faulty, I can leave my cx5 for a week and still have a enough vacuum in the system. I think this dealer should be head slapped and told this is normal

Battery maybe getting low

Help both key fobs quit, 1 works occassionally, 1 not at all. When started with me brake was extremely had to push but car had been driven less than 12 hours previously. I have a hard time believing it's the batteries since both started acting up within 30 days. Any suggestions appreciated.

I have a 2015 cx-5. Mine is not working now. It has been getting worse over the last few months. I literally need to bang it on my steering wheel and mess with it for 10 minutes - 30minutes. Took it to my original dealer who is no longer Mazda, and they said the battery and the key fob were working fine. They told me I had to go to a certified Mazda Dealer in another town to get it looked at. It is so annoying! I have loved my car until this started happening.

Put your key on the dash , this has solved the starting. Problem

I have a 2016 Mazda cx-5 with 4,500 miles and it won't start. A image on the dashboard comes out and it says keyless system malfunction. What is wrong.

Alex, what did you do....since it has been 3 months. My car was driven. Parked. Sat for about 3 hours. Would not start. This was yesterday. Mazda CX5 2016. I was out of town and had to get a ride home. This is very frustrating. A relative has put new batteries in the fob. He has tried to start it like the internet says. Now, the lights will not come on. We cannot lock it. Cannot get into the trunk. ETC, ETC. This is really sad that cars are designed like this. Thank you for any help you can give.

Chip or sensor that is behind the ignition isn't "reading" the key fob signal. It is probably needing to be reset or replaced. I have to literally lay the fob on the start button to fire up the car. I have appointment at dealer monday for them to verify my thinking.

My Dealer gave a few suggestions. My car dashboard constantly says "key battery low" and after a while of this I can no longer open the door from the handle, have to push the unlock button on the fob (sometimes more than once), and have to hold the fob up next to the start button on the dash to start the car. It's also very annoyingly easy to lock my keys in the car since it doesn't recognize the key. When I put new batteries in my fob, it starts all over with low battery again in about 2 weeks. It seems there would be a problem in the car sensor system, but they only had suggestions for the fob. Let's hope Dorothy above got a good answer to share from her appointment! Suggestions: 1. Make sure you have taken the plastic cover off the back of the battery itself. 2. Make sure you're using fresh batteries. If you purchase one that's been on the shelf for a LONG time it may not have enough power. They said even 2.99 when it is supposed to be 3 volts will cause it to not work. 3. Pull the 2 little metal tabs that make the connection in the battery compartment up some. Over time they get smashed down. (DING DING DING - I did this and now my fob is opening my car door and starting my car normally, but the dash will still say "low battery." And yes, I did check my batteries and they are at 3v.) 4. Be sure to carry your fob loosely, not in tight pockets or spaces as the buttons can get depressed and run your fob battery down. Also, on another note, my car is only 3 years old and even though the manufacture battery should last about 5 years, anytime I leave it for 10+ days the battery dies. My dealer said this can be common!! There are a lot of computers and the alarm system that can drain it. Also, be sure to unplug any phone cords as they will continue to draw power even when not attached to your phone, ipad, etc.

I recently lost my key fob(2016 cx5). I am thinking I accidentally threw it away. When I get in my car and press the brake, the key indicator light flashes green. What does this mean? I am thinking it is somewhere close since the light is green? Any help is appreciated

This just happened to me, UNPLUG BATTERY TERMINAL!! Basically it restarts the whole car and clears the warning. Started right up!

Quite the puzzle. New batteries, numerous blogs, dealers, all of the above. After 2 months I finally figured it out. The Mazda fob calls for a 2025 battery. It is actually millimeters too small for the fob casing. It does not consistently hit the connector points. I found this out by pushing the 2025 forward with my finger on the exposed battery with it working and not working when the casing lid was applied. The 2032's DO fit. It always makes a nice connection, will actually last longer, and works great. The 2032's will not have a negative affect on the fob or the transmitter. I don't know what happened in that Japanese factory but, O' what a relief it is! Good luck.❤️ Gina.

Thank you for this suggestion. We will try the different battery. It’s been extremely frustrating, not to mention unsafe when our daughter can’t start the car after work. We’ve gone through so many batteries, replacing almost monthly.

Thank you Guru1FNK4. I have been searching and trying every suggestion for the last month, but nothing worked until I found your post. so I changed the battery to 2032 then it works great. thankyou.

Did you try to check the switch tha is on de shift knob? when you put the car in parking mode the shft knob depress a little switch that cut off electricity all devices and power on the sistem that controls the wireless function of the fob. When it is defective your car do weird thing with the fob and his commands. Try to move the shift knob firmly on the parking mode to de left. It it return to the normal fuctionality then you need to chage the entire witch. This is the part: Mazda AT Shifter Switch 2013 2014 CX-5 2014 Mazda 6 KDY046040

Hi everyone. i have a 2016 CX-5 and was having many of the issues described in this thread. the fob was locking/unlocking the doors but would not start the car. when i pressed break pedal and pushed start button the lights on the dash would go crazy and i'd get every flashing alert possible. changed fob battery twice, nothing working. finally.....even though the cars interior lights were working i tried jumping the car battery. that did it! remember - even though the alerts and lights in the car still function, you might still need to jump the car and run more juice through the battery.

Any update sbertuglia? Happening to me now

My daughter owns a 2013 CX5 and just recently started having this problem with the ignition switch not starting.. the fab key opens the car and the ignition switch turns green but nothing happens. I’m going to have to try and switch the battery on the key fab to 2032 and see what happens.. Will update once we do that to see if the car starts..:)

Well I changed the battery on the remote and the issues persisted.. I ended up changing the car battery and now its working fine..very weird!!

Was having same issues with key not being detected or lock/unlock. I took Guru1FNK4 suggestion and it worked right away. Doors locked and unlocked on first press, car started w/o “key not detected warning” and auto lock started working again. I put the 2025 battery back in and used a small rubber bumper to make the o-ring cover press the battery down more.

I had a low battery 2014 key fob which stopped working completely after installation of the new battery. I pulled the key fob apart and discover that the new battery had a thin layer of tap covering the back side which I hadn't noticed. Pulled the tape off, reinstalled the battery and everything worked great. Feeling pretty silly but it really had me stumped.