Mazda Recalls CX-90 PHEV Over Improper Failsafe Logic

November 2022 is when Mazda received the first report alleging the complete shutdown of the four-cylinder engine and electric motor. Come February 2023, the company identified the root cause as improper failsafe logic for the powertrain control module and engine control module.

For some reason or another, Mazda continued looking into this issue through October 2023 instead of coming up with a remedy earlier this year. What is especially regrettable about Mazda’s lack of proactive action is that CX-90 PHEV vehicles produced at the Hofu plant after June 20 sport revised failsafe logic for both the PCM and ECU.

Mere days ago, Mazda held a quality audit committee meeting during which a field action was approved for potentially affected vehicles. No fewer than 4,252 examples of the breed are recalled in the United States and US federalized territories. Mazda isn’t aware of any reports of accident related to the aforementioned issue.

Increased PHEV system inverter temperature will activate failsafe mode, and there is no warning prior to activation. Otherwise put, a complete and unexpected loss of drive power increases the risk of a crash. How does the remedy software differ from the original version? For starters, the driver is notified by warning lights and messages in the instrument cluster if the inverter gets too hot. Next up, it will shut off the electric motor. The big change, however, is that the combustion engine won’t shut off in the event of abnormally high PHEV system inverter temperatures.

One has to ask themselves, why didn’t Mazda think of this self-evident solution in the first place? On the other hand, bear in mind that Mazda has little in the way of experience with plug-in hybrids and electric vehicles. The Hiroshima-based automaker is way behind the curve, and the automaker doesn’t appear to understand how behind it really is. The MX-30 R-EV range-extender hybrid is the perfect example in this regard, a needlessly complicated setup that incorporates a rotary engine rather than a more frugal and proven technology. Think Atkinson-cycle powerplants from Toyota such as the inline-four M20A-FXS found in the Prius and A25A-FXS in the Venza.

In any case, owners will be informed by first-class mail on or about December 22. In the meantime, owners can verify whether their three-row sport utility vehicles are recalled or not by running the VIN on the NHTSA’s website.

Equipped with a 2.5-liter I4, the CX-90 PHEV further sports a 17.8-kWh battery pack as opposed to 0.33 kWh for the 3.3-liter I6 mild-hybrid powertrain. A naturally-aspirated mill as opposed to a single turbo for the sixer, the inline-four engine is assisted by a permanent-magnet synchronous electric motor in the eight-speed tranny.

Mazda claims 26 miles or 42 kilometers of electric driving range, along with 25 miles per gallon (9.4 liters per 100 kilometers) of combined fuel economy from the 2.5-liter powerplant alone. Coincidentally, the 3.3er is also rated at 25 miles per every gallon on the combined test cycle.