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

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.

My car was in the shop in November 2018. It was during one of my many trips to the dealership back then that the service manager showed me a technical bulletin that they had just received concerning this situation. I am sorry but I have no idea what the number of the bulletin is or was.
 
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...
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. So, your assumption is correct about the oil pressure. My dealership showed me the pictures of the rocker arm out of its position.
 

yugrus

Contributor
:
CX-5 GT
I still wonder how the engine runs fine in idle with dislodged rocker arm... And how the arm is allowed to slip on the shaft. Perhaps, that lateral movement is by design to shut the cylinder off by missing the valve. And increased oil pressure is supposed to bring it back over the valve.
Ok, I think it now makes sense, if that's the case. Rocker arm slipped to de-activate the cylinder on the highway, then there wasn't enough oil pressure to get it back over the valve when full power is commanded. Fuel is injected, but no combustion. PCM hits panic button, lighting up the dash and invoking limp mode.
On restart the PCM commands full oil pressure, the arm gets back over the valve.
 

yugrus

Contributor
:
CX-5 GT
I thought you could disable cylinder deactivation if you didnt want to use it???
You can, in GM and Chrysler vehicles. I did just that in my Tahoe, which will not see 4-cyl mode untill I decide to despose of the rig. I haven't heard about Mazda solution yet. But I'm sure it's coming.
 
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I still wonder how the engine runs fine in idle with dislodged rocker arm... And how the arm is allowed to slip on the shaft. Perhaps, that lateral movement is by design to shut the cylinder off by missing the valve. And increased oil pressure is supposed to bring it back over the valve.
Ok, I think it now makes sense, if that's the case. Rocker arm slipped to de-activate the cylinder on the highway, then there wasn't enough oil pressure to get it back over the valve when full power is commanded. Fuel is injected, but no combustion. PCM hits panic button, lighting up the dash and invoking limp mode.
On restart the PCM commands full oil pressure, the arm gets back over the valve.

The rocker arm literally falls off. It was laying down by the valve port. The engine runs fine during idle and lower RPMs due to the fact that it has four valves per cylinder. The computer only senses a problem at higher revs. At this point it senses a lean situation on #4 cylinder (in my case) because one intake valve is not stroking. This is what makes this situation so deadly. You as the driver have no indication or idea that you have a problem until you are reving the engine and need the power and suddenly the computer senses trouble and throws the engine into limp mode. As my first post indicated, it happened to us when we were passing an 18 wheeler at night. This is what I was, and still am so furious about. We as the drivers of these vehicles have no idea something is wrong untill it is too late. This happened months ago and I am bringing this up now again because I just took our car in for an oil change and talked with the service manager about all of this again. He stated that since my car left and one other one they had to change the engine in, there has been nothing from corporate about this situation. Total silence!! So I figured I would try to see if I could get the word out to people about this since there has been no recall or really any action from Mazda. I am concerned that there may have been people already in accidents or possibly killed due to this issue. This could easily cause a head-on collision and at that point people would just think it was driver error or ignorance not knowing that the cause was mechanical failure.
 
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2018 CX-5 GT PP
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?

What does this have to do with the CD feature? The OP stated he was driving in conditions where it wouldn't have been on. He's describing something very different. Misleading title.
 

yugrus

Contributor
:
CX-5 GT
I wholeheartedly thank you for this effort. Looks like the proverbial "don't lose your face" Japanese attitude. Rocker arm falling off completely, eh... If Mazda has registered in automotive scale of things, this would have been a scandal...
 

yugrus

Contributor
:
CX-5 GT
What does this have to do with the CD feature? The OP stated he was driving in conditions where it wouldn't have been on. He's describing something very different. Misleading title.
I don't think so. He was on the highway, following the rig. Steady high-speed, low RPM situation. Cylinder deactivation must have been on before the ordeal happened.
 
What does this have to do with the CD feature? The OP stated he was driving in conditions where it wouldn't have been on. He's describing something very different. Misleading title.

It during cylinder deactivation that the rocker arm falls off. So once that rocker arm is off you have a serious situation that you have no indiction of. A few days later you may be driving and need to pass a vehicle. At this point you accelerate and the RPMs hit about 5000 and all of a sudden your car goes into limp mode. You cannot rev the engine past approx. 2500 RPMs. Deadly scenario if your are stuck in the oncoming lane with oncoming trffic and no acceleration to get you out of the way.
 

yugrus

Contributor
:
CX-5 GT
Two rocker arms operate two intake valves. One falls off the shaft. Another one operates its valve in idle and low-power operation. Everything is cool and dandy. But when you request full power, it is nowhere to be found, because the second intake valve is closed shut.
 
Please, if you have one of these vehicles 2018 cx-5 or Mazda 6, your car has cylinder deactivation and you need to take it in and have them remove the valve cover and visually inspect to make sure all is well. And demand they reflash your PCM! The 2019s also have cylinder dactivation unless you have the Turbo engine. Remember, they told me that one of their two PCM suppliers has the wrong program. This means that it is possible that half of or maybe more than hal off all of these vehicles are driving around with this problem and people don*t even know it. Which means that even if you don*t drive one you could end up meeting one in your lane someday.
 
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Two rocker arms operate two intake valves. One falls off the shaft. Another one operates its valve in idle and low-power operation. Everything is cool and dandy. But when you request full power, it is nowhere to be found, because the second intake valve is closed shut.

This is exactly right. Now you understand what I am saying.
 

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