Function Explanation (DTC Detection Outline)

• The PCM detects the oxygen concentration in the exhaust gas based on the A/F sensor signal. By intentionally increasing/decreasing the fuel injection amount, the PCM controls the oxygen concentration in the exhaust gas to rich or lean and monitors the response speed of the A/F sensor to sudden changes in the oxygen concentration. If the response speed of the signal input from the A/F sensor is slow while switching repeatedly between rich and lean, the PCM determines an A/F sensor malfunction and stores a DTC.

Fig 1: DTC Detection Outline Timing Pattern

Courtesy of MAZDA MOTORS CORP.