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Cylinder Deactivation

:
2015 Mazda 6
Just saw this: Seems like it's legit and could answer a lot of the CD issues/questions consumers have. Will this stop the vibrations? Will there be an option to deactivate the CD completely...who knows?

There is an interesting story behind this recall. There are two PCM (powertrain control module) suppliers contracted by Mazda for their engines, and for whatever reason one of them did not apply the last finalized production software update for vehicles with cylinder deactivation (CD). The software controls the variable valve actuation when the engine is switching from CD 2 cylinder mode back to normal 4 cylinder operation. As a result, any of the CD vehicles that had this model of PCM installed were susceptible to stalling and potential engine damage. However, because not all CD vehicles were affected it took Mazda a while to determine the cause as they did not initially realize that one supplier was shipping PCMs with an outdated software version. The fix in the end is simply a PCM software upgrade performed by the dealer. In rare cases if a valve made contact with another part of the engine (ie: piston) when the system malfunctioned a whole new engine could be required due to physical damage of the valve rocker arm components.

As for the rationale behind CD, although it may seem silly for only 1 or 2 mpg gain, when multiplied by thousands of vehicles it significantly benefits Mazdas overall CAFE score. Mazda is a small manufacturer that has no hybrid vehicles to speak of to help boost their CAFE average score.


https://static.nhtsa.gov/odi/rcl/2019/RCLRPT-19V497-6744.PDF
 

erhayes

Contributor
:
Mazda CX-5 FWD Touring
I suspect the cylinder deactivation would result in a 0.1 to 0.2 mpg increase and not a 1 to 2. JMT. Ed
 
:
2017 CX5 AWD Touring
It's a very complicated system to gain very little MPG and creates tons of reliability problems, including catastrophic engine failure. In other words, it's a stupid design and idea.

It's like Boeing's Max Jet design which killed hundreds of people and grounded thousands of planes indefinitely. They also blame a software issue. Although the design of the plane was flawed from an engineering basis and Boeing sought to use software nanny's to compensate for the flawed design. Overly complicating the plane and causing crashes and deaths.
 
Wow huge exaggeration comparing CD to the 737 Max which has killed hundreds of people.

The CD issue with programming has been resolved, the initial reports of problems were few and resolved under warranty.
My wifes 2018 CX5 has been rock solid reliable with 33k miles on it and I just purchased a pre-owned 2019 with 14k miles on it. Our family has no concerns of catastrophic engine failure.
If this was a rampant problem you would have thousands of reports by now
 
:
Ottawa, Ontario
:
17 Mazda 6 GT
It's like Boeing's Max Jet design which killed hundreds of people and grounded thousands of planes indefinitely. They also blame a software issue. Although the design of the plane was flawed from an engineering basis and Boeing sought to use software nanny's to compensate for the flawed design.
There were roughly 370 planes in service worldwide when they were grounded. Not thousands.
There were a lot more than that on order and being built, but those didn't go into service.
Boeing has also stopped building the plane until they sort it out.
Having said that, the design is still flawed, and it killed a lot of people.
No amount of software tweaks will fix a poorly designed and engineered plane.
I just read that as they were testing the new programming, a completely different software problem popped up. Now they have another problem to fix.
It will be a while before this thing flies again.
 

Avoidin Deer

Zoom Zoom, baby
Contributor
:
Central Virginia
:
2019 CX-5 Reserve
Just saw this: Seems like it's legit and could answer a lot of the CD issues/questions consumers have. Will this stop the vibrations? Will there be an option to deactivate the CD completely...who knows?

There is an interesting story behind this recall. There are two PCM (powertrain control module) suppliers contracted by Mazda for their engines, and for whatever reason one of them did not apply the last finalized production software update for vehicles with cylinder deactivation (CD). The software controls the variable valve actuation when the engine is switching from CD 2 cylinder mode back to normal 4 cylinder operation. As a result, any of the CD vehicles that had this model of PCM installed were susceptible to stalling and potential engine damage. However, because not all CD vehicles were affected it took Mazda a while to determine the cause as they did not initially realize that one supplier was shipping PCMs with an outdated software version. The fix in the end is simply a PCM software upgrade performed by the dealer. In rare cases if a valve made contact with another part of the engine (ie: piston) when the system malfunctioned a whole new engine could be required due to physical damage of the valve rocker arm components.

As for the rationale behind CD, although it may seem silly for only 1 or 2 mpg gain, when multiplied by thousands of vehicles it significantly benefits Mazdas overall CAFE score. Mazda is a small manufacturer that has no hybrid vehicles to speak of to help boost their CAFE average score.


https://static.nhtsa.gov/odi/rcl/2019/RCLRPT-19V497-6744.PDF
There's nothing in that Recall Report you linked that gives the backstory.

Where did you read that backstory?
 

Chris_Top_Her

Banned
Moderator
Contributor
:
San Antonio, Texas
:
'15 CX-5 Miata AWD
Fleet mileage -- reason for CD which will reduce long term reliability. Reason for 0w20 which is more susceptible to blow by and oil consumption, and less durable
 

Who has a CX-5 and a Miata?

  • Yes, an ND MX-5 Miata

    Votes: 8 11.8%
  • Yes, an Older Gen MX-5 Miata

    Votes: 20 29.4%
  • Yes, more than one actually...

    Votes: 2 2.9%
  • No but I'm in the market for one...

    Votes: 4 5.9%
  • No

    Votes: 34 50.0%
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