Function Explanation (DTC Detection Outline)

WARNING: This page is about a different car, the 2017 Mazda 3. However, it is still accessible from the selected car via links, so may be relevant.

The PCM detects the oxygen concentration in the exhaust gas from the A/F sensor signal and performs fuel injection amount feedback to maintain the optimum air/fuel ratio. If a condition in which the feedback correction amount is large (fuel injection amount being increased) continues for the specified time, a feedback correction amount malfunction is determined, and a DTC is stored. The feedback correction amount has a "Fuel feedback correction amount" for the air/fuel ratio and a "Fuel learning correction amount" for fuel injector deterioration over time.
"Fuel feedback correction amount (SHRTFT1)" and "Fuel learning correction amount (LONGFT1)" can be verified from the M-MDS PID item.

The sum of the fuel feedback correction amount (SHRTFT1) and the fuel learning correction amount (LONGFT1) is the specified value (30 %) or more, and 10 s or more have elapsed with the fuel learning correction amount (LONGFT1) at the specified value (15 %) or more. Engine coolant temperature:0-45 °C {32-113 °F}, 60 °C {140 °F} or more

Fig 1: Sum Of Fuel Feedback Correction Amount And Fuel Learning Correction Amount Timing Graph
Courtesy of MAZDA MOTORS CORP.
Fuel learning correction amount (LONGFT1) at specified value (25%) or more. Engine coolant temperature:0-45 °C {32-113 °F}, 60 °C {140 °F} or more

Fig 2: Fuel Learning Correction Amount Timing Pattern

Courtesy of MAZDA MOTORS CORP.