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took Mazda a while to determine the cause as they did not initially realize that one supplier was shipping PCMs with an outdated software version.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 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took Mazda a while to determine the cause as they did not initially realize that one supplier was shipping PCMs with an outdated software version.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