Function Explanation (DTC Detection Outline)

• The PCM compares the target EGR flow volume with the estimated EGR flow volume and performs diagnosis of the EGR system.
• The PCM opens the EGR valve when all of the preconditions are met. The PCM compares the target EGR flow volume with the estimated EGR flow volume at that time, if the estimated EGR flow volume is smaller than the target EGR flow volume, a malfunction is determined.
• The PCM performs diagnosis when each of the preconditions during drive cycle is met. If a malfunction is detected, the malfunction detection counter begins counting up. The value of the malfunction detection counter is maintained while the preconditions are not being met. If the cumulative value of the malfunction detection counter exceeds the threshold during the first drive cycle, a malfunction is determined and a pending code is stored.
• If the calculated value of the malfunction detection counter during one drive cycle exceeds the threshold, the PCM determines a malfunction, stores a DTC and turns on the check engine light.

Courtesy of MAZDA MOTORS CORP.