Some 2012-2013 Mazda3 SKYACTIV models, 2013-later CX-5, 2016-later MX-5 and 2016 CX-9 vehicles may experience the check engine light on with DTC P0171 (fuel trim too lean) and possibly P030X (misfire) set.
1. Inspect the air box/air filter for proper fitment. Repair as needed.
2. Inspect the MAF for correct operation. Repair as needed.
3. Inspect the A/F sensor for correct operation. Repair as needed.
4. Inspect the fuel trims during normal engine idle condition.
If fuel trims are normal after performing steps one through three, the repair is complete. If trims are abnormal, replace the fuel injectors. Note: P0171 will set while the engine is idling or the vehicle is driven and the fuel feedback correction amount reaches the upper limit (25% or more) for 20 seconds or more.
