Function Explanation (DTC Detection Outline)

With the preconditions met, the PCM verifies the conformity of the actual timing relative to the target valve timing. If it does not conform to the normal determination range (difference between target valve timing and actual valve timing is 20 degrees or less) during the malfunction determination period (approx. 5 s) , even if the target valve timing is set to the retard side, the PCM determines an excess advance malfunction condition and stores a DTC.

Fig 1: Valve Timing Graph (DTC Detection Outline)
Courtesy of MAZDA MOTORS CORP.