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Thread: Dangerous cylinder deactivation trouble on 2018 CX-5 and 6 models

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    Dangerous cylinder deactivation trouble on 2018 CX-5 and 6 models

    This is a long read but hopefully it will get the attention of the right people and quite possibly save a life.

    My wife and I own a 2018 Mazda CX-5 Grand Touring. We purchased the vehicle to replace our 2014 Mazda 6 GT. Being the proud Grandparents of two beautiful little girls, we wanted a vehicle that was easier for us to get them and their carseats in and out of. The CX-5 is perfect for that and we were extremely happy with the vehicle until it almost caused us to be in an accident that could have killed us both.

    For the year model 2018, Mazda added cylinder deactivation to the engines that are installed in both the CX-5 and the Mazda 6 models. Unfortunately this system is what caused the trouble for us and, at last count, at least 26 other customers that Mazda has confirmed.

    My wife and I were on vacation following a car on a curvy mountain road. I had the CX-5 in Sport mode. At one point the vehicle in front of us pulled over for us to go around them. As I accelerated to go around the vehicle, our car cut out and went into ďlimp modeĒ. The dash lit up with alarms and we had to pull to the side of the road due the limp mode not allowing the engine to rev past 2500 rpm. Our vehicle is equipped with a camera for automatic braking, lane identification, and cruise control. The alarm on our dash read ď Automatic braking system failureĒ. This alarm led me to believe our trouble was with the camera. We were able to reset the alarm and the limp mode by simply shutting the car down and restarting it. Upon restarting the car, all alarms would clear and the engine would rev as normal. We continued on our way with intentions of taking the vehicle to the shop once we got home from our vacation thinking that it may just be a glitch with the camera. We were wrong! This happened 2 more times on our trip before the incident that we will never forget.

    The previous times that we had trouble were all in daylight hours and accelerating around a vehicle to pass. On this final time it was dark and we were following a semi truck on a two lane highway in central Oregon. I had the opportunity to pass the semi. I accelerated and moved into the oncoming lane to go around the truck and trailer. Just as we were moving back into the lane in front of the semi, the car cut out and went into limp mode again! We basically were straddling the center line with a dead vehicle and an 80,000 lbs semi getting ready to roll over the top of us or push us off of the road. Luckily no cars were coming from the other direction. The truck driver slowed down enough for us to limp ( going 65 mph) across in front of him to the edge of the road and stop. At this point we realized that it wasnít the camera but had something to do with accelerating the engine. We reset the vehicle again and didnít take the car over 4000 rpm for the rest of the way home.

    We were able to take the car to the dealership 2 days later. I described the issue we were having and that we thought it was something with the engine. They took the car into the shop and after an hr came and told me that the problem was fixed. They had called Mazda and were told the issue was with the camera. They reprogrammed the camera controller upon Mazda recommendations. I argued with them and explained again what we had seen and that we thought the trouble was with the engine. They said that I had to take the car and if it happened again to bring it back. I told them that the car was unsafe and it was poor of Mazda to think a customer should take an unsafe vehicle on the road. I left the lot and went straight to the freeway and duplicated the problem again. This time, as I sat on the shoulder of the freeway, I videoed the dash for them to see. Reset the car and headed right back to the dealership. They gave me a loaner (another CX-5) and said they would call me when they had it figured out. Two hrs later the service manager called me and said they had it figured out. A rocker arm had fallen off of cylinder #4 and they were going to be replacing my engine. They had called Mazda again and the engineers had told them to remove the valve cover and look for this issue. Mazda had seen it before and our car was number 19 with this issue. When I asked how that was even possible the dealership couldnít answer my question. They had my car for a couple of weeks and replaced the engine. When we went to pick it up, they still couldnít tell me why it happened. We refused to take the car until we knew why it happened and if the issue was fixed. The service manager agreed with us and kept us in his loaner for another week. At this point I told the service manager that I wanted to talk to someone at Mazda corporate to see if I could get some info from them. He gave me their number and I called them the next day. I explained the whole thing to them and how I didnít feel safe taking a vehicle with no explanation as to what the cause was. A case file was opened with them and they stated that they would be keeping me informed. A few days later I received a call from corporate customer service with an explanation. They told me the problem was caused by a low oil pressure on cylinder #4 which enabled the rocker arm to dislodge. The remedy was to reprogram the main PCM to not allow the pressure drop. Mazda corporate was sending the tool to my dealership to reprogram the PCM. This was done and supposedly our car is now fixed. Now, here is the huge problem and why this could possibly kill someone or may have already done so. There is no indication as to when this rocker arm fell off. The computer senses nothing. It could have been off for months! Once that rocker arm falls off the car still runs fine, as far as the computer is concerned. On our vehicle it was a rocker arm on an intake valve. The computer senses nothing wrong with that cylinder until the rpms get high enough that the cylinder canít keep up the burn and then it finally throws the cylinder misfire code and sends the engine to limp mode to protect the engine. This is deadly! It happened to us when we were passing. We need the engine at that point. If it miss fires on one cylinder you probably can still get out of harms way if need be. But you certainly canít when it goes into limp mode.

    When we went to pick up our vehicle, I asked the service manager if the reprogrammed all of their cars on the lot that have the same engine as ours. He said they had not since Mazda didnít recommend it. This makes no sense. Why would they not reprogram every vehicle to prevent this problem?! I also told them that the logic of sending the car to limp mode at the rpm is going to kill someone and needed to be changed. We took our car and went home. This was on a Friday (black Friday actually) and this ate at me so bad all weekend that I went back to the dealership the following week to demand to talk with someone with some technical background in corporate to express my concerns about the safety of these vehicles. Before he got me in touch with corporate, the service manager told me that Mazda has found the source of the problem. Apparently Mazda has 2 suppliers of PCMs. One of the suppliers has the wrong program installed on all of their PCMs that they have sold to Mazda! Mazda is currently trying to figure out what vehicles have these PCMs installed so they can get in touch with the owners. When he told me this I lost it! Again I asked him why the heck Mazda doesnít just reprogram all vehicles on every lot and recall every one of these vehicles so they can reprogram them and be done with it. They are going to wait to try to figure out which vehicles are bad? Meanwhile women and children are driving around in these cars and they may have a huge problem and not even know it!! I was able to talk with the west regional tech support. (John). Expressed my concerns, he agreed with me but stated that possibly Mazda was going to collect some data from the cars that have been reprogrammed to make sure that this is the fix. I told him that I wasnít going to be a Guinea pig for Mazda by ďtestingĒ their fix for them and end up wrapped around a pole somewhere because the fix wasnít right!!

    I have contacted Mazda corporate customer service again and expressed my concerns about recalling all of these cars and reprogramming the PCM and changing the logic to not have it go into limp mode at those higher RPMs. I was told by them that Mazda will not be doing that and my car is considered to be fixed.

    So we now have a car that may be fixed but gives no indication of a problem if this happens again. My wife is afraid to take the Grandchildren in it because she feels it isnít safe.

    Please tell anyone you know who has one of these vehicles to get in into the shop asap. There is a technical service bulletin that Mazda just released to the dealerships for this issue.

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    I'm sorry for your troubles and thank you for a good job getting to the bottom of it.
    Here we go, to the previous discussion about cylinder de-activation. All this nonsense for what, like 0.5 mph gain at the right conditions?
    I don't really follow their explanation about the rocker falling off, just can't picture this failure. I think most likely they were talking about collapsed lifter because of low oil pressure. The oil pump produces variable pressure, again, to save fuel.
    What a mess...

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    Arrow Dangerous cylinder deactivation trouble on 2018 CX-5 and 6 models

    Quote Originally Posted by yugrus View Post
    I'm sorry for your troubles and thank you for a good job getting to the bottom of it.
    Here we go, to the previous discussion about cylinder de-activation. All this nonsense for what, like 0.5 mph gain at the right conditions?
    I don't really follow their explanation about the rocker falling off, just can't picture this failure. I think most likely they were talking about collapsed lifter because of low oil pressure. The oil pump produces variable pressure, again, to save fuel.
    What a mess...
    Where were you when I was almost the only one here criticizing cylinder deactivation Mazda suddenly implemented on 2018 CX-5?

    Originally I planned to get a new 2018 CX-5 a while ago, but I changed my mind only because the cylinder deactivation. I bought a 2018 Mazda2 instead which definitely has no cylinder deactivation!

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    Quote Originally Posted by yrwei52 View Post
    Where were you when I was almost the only one here criticizing cylinder deactivation Mazda suddenly implemented on 2018 CX-5?

    Originally I planned to get a new 2018 CX-5 a while ago, but I changed my mind only because the cylinder deactivation. I bought a 2018 Mazda2 instead which definitely has no cylinder deactivation!
    You bought a 2018 mazda2 in the USA? Did you import it from PR?

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    Also glad I don't have that novelty on my engine. And luckily it's not on the turboh engines. Good thing it happened in warranty!
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    bought a new 2019 beginning of april and not once has anyone from mazda said
    anything to me about this cylinder de-activation. I didn't even know about it till
    just now reading this thread !
    I don't think I would have bought it had I known..... , same with getting
    harley.. but you can activate/de-activate that on hd easily enough....

    Thought the engine was acting wierd when driving around town......slow speeds.
    Thought is was just the gearing ........but it makes sense that it is the de-activation
    kicking in .........

    thanks op for making me aware of this....

    Is there a website to view the service bulletin ?

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    Quote Originally Posted by yrwei52 View Post
    Where were you when I was almost the only one here criticizing cylinder deactivation Mazda suddenly implemented on 2018
    Yo, I was actually the first one to start the whole ordeal!

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    Arrow Dangerous cylinder deactivation trouble on 2018 CX-5 and 6 models

    Quote Originally Posted by Go Hawks View Post
    This is a long read but hopefully it will get the attention of the right people and quite possibly save a life.

    My wife and I own a 2018 Mazda CX-5 Grand Touring. We purchased the vehicle to replace our 2014 Mazda 6 GT. Being the proud Grandparents of two beautiful little girls, we wanted a vehicle that was easier for us to get them and their carseats in and out of. The CX-5 is perfect for that and we were extremely happy with the vehicle until it almost caused us to be in an accident that could have killed us both.

    For the year model 2018, Mazda added cylinder deactivation to the engines that are installed in both the CX-5 and the Mazda 6 models. Unfortunately this system is what caused the trouble for us and, at last count, at least 26 other customers that Mazda has confirmed.
    Ö

    So we now have a car that may be fixed but gives no indication of a problem if this happens again. My wife is afraid to take the Grandchildren in it because she feels it isnít safe.

    Please tell anyone you know who has one of these vehicles to get in into the shop asap. There is a technical service bulletin that Mazda just released to the dealerships for this issue.
    I'm sorry too to hear the story and thanks for letting us know the potential problem on cylinder deactivation.

    You could be one of the guinea pigs for Mazda at this time to fix this problem. Automobile is very complicated nowadays. Almost every car manufacture will start with software fix for problems if possible as it's the cheapest way to do. Sometimes they even modify the operating range or limits to mask the problem. If that doesn't work, then modify the hardware is the last resort as it's getting expensive. The dragging problem on 2016 CX-5 EPB is a perfect example where Mazda took 3 tries, hence 3 revisions on the TSB, and eventually found the root of the problem. Mazda at first was to replace the EPB control module with updated firmware (sounded familiar?). Then they updated the firmware the second time. And eventually those software changes wouldn't work and Mazda had to redesign a couple of internal EPB parts for the rear brake caliper to fix the problem.

    Cylinder deactivation designed by Mazda is a very complicated system where many engine and transmission parts got redesigned. Like yugrus, I wonder is it really worth it though?

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    Quote Originally Posted by Chris_Top_Her View Post
    You bought a 2018 mazda2 in the USA? Did you import it from PR?
    Uh ... a 2018 Toyota Yaris iA ...

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    Quote Originally Posted by yrwei52 View Post
    Uh * a 2018 Toyota Yaris iA *
    Oh I see. Because you can legally get a 2016+ mz2 from PR to the mainland
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    Quote Originally Posted by yugrus View Post
    Yo, I was actually the first one to start the whole ordeal!
    Sorry, I must have missed that somehow ...

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    The rocker arm is dislodged by the cam lobe due to low oil pressure on the lifter. This low pressure allows for slop of the rocker arm. My dealership showed me the pictures of the rocker arm out of its position.

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    Quote Originally Posted by Go Hawks View Post
    The rocker arm is dislodged by the cam lobe due to low oil pressure on the lifter. This low pressure allows for slop of the rocker arm. My dealership showed me the pictures of the rocker arm out of its position.
    Well, at least they didn't follow GM debacle step-by-step then. Still beats me how would the rocker be allowed to slip laterally. How would the engine run normally, even in idle, with intake valve shut all the way...
    That's a sloppy design for sure.
    Last edited by yugrus; 05-03-2019 at 11:32 PM.

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    By the way, I can't find that TSB on any of the sources I have access to yet. Maybe too new and hot.
    Well, there is one, CHECK ENGINE LIGHT ON WITH DTC P0524. It deals with the PCM programming where its oil pressure ramp-up is too slow under certain conditions. It is dated Oct 18, 2018.
    Last edited by yugrus; 05-04-2019 at 06:48 AM.

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    So the two engine choices for the 2019 are NA with CD that sometimes craps out OR a turbo that sometimes craps out. WTF, Mazda?
    Glad I got a 17, for now anyway.

    Well done, OP, sticking to your guns and reading them the riot act.

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