Some 2013-2023 Mazda CX-5, 2016-2022 MX-5, 201202013 Mazda3 Skyactiv, 2014-2023 Mazda3, 2016-2019 CX-9, 2014-2021 Mazda6, and 2016-2019 CX-3 vehicles may experience a MIL on with DTC P0171 (fuel trim too lean) and possibly P030X (misfire).
Inspect the airbox/filter for proper fitment. Inspect the MAF for correct operation. Inspect the A/F sensor for correct operation. Inspect the fuel trims during normal engine idle conditions.
If fuel trims are normal after the previous inspections/repairs, the repair is complete. If fuel trims remain abnormal, replace the fuel injectors.