Function Explanation (DTC Detection Outline)

WARNING: This page is about a different car, the 2020 Mazda CX-30. However, it is still accessible from the selected car via links, so may be relevant.

If both the intake valve and exhaust valve for the deactivated cylinders open mistakenly, the intake air flows to the exhaust pipe and the A/F in the exhaust gas changes to lean. If a large A/F fluctuation during cylinder deactivation is determined, the PCM determines that both the intake valve and exhaust valve for the No. 1 or 4 cylinder are open, and stores a DTC.