Function Explanation (DTC Detection Outline)

The PCM diagnoses the turbo system performance by comparing the target air charging pressure with the actual.
The PCM uses the manifold absolute pressure sensor to monitor the intake manifold pressure during boost control as the actual air charging pressure.
When the monitoring conditions are met during boost control, the PCM compares the target air charging pressure with the actual. If the actual air charging pressure is higher than the specification for the target air charging pressure, the PCM determines an excess air charging malfunction.
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 PCM determines that the malfunction recurs from the next drive cycle and thereafter, it stores a DTC and turns on the check engine light.

Fig 1: Timing Value Graph

Courtesy of MAZDA MOTORS CORP.