On-Board Diagnosis Logic
ON-BOARD DIAGNOSIS LOGICIf misfire occurs, the engine speed will be fluctuated. If the fluctuation is detected by crankshaft position sensor (OBD), the misfire is diagnosed. The misfire detection logic consists of the following two criteria.
1. A CRITERION (One Trip Detection Logic): When the misfire is detected which will damage the three way catalyst by overheating, the malfunction indicator lamp will start blinking even if the drive is the first trip. In this criterion, Engine Control Module (ECM) monitors the misfire for each 200 revolutions of the engine. If the misfire frequency decreases to the level that will not damage the three way catalyst, the blinking of the indicator lamp will turn to the lighting up. (After the first trip detection, the indicator lamp will light up from the engine starting till the next trip misfire detection which will damage the three way catalyst.)
2. B CRITERION (Two Trip Detection Logic): When a misfire which will not damage the three way catalyst (but will affect the emission deterioration) occurs in this criteria, the malfunction indicator lamp will light up based on the two trip detection logic. In this criterion, ECM monitors the misfire for each 1,000 revolutions of the engine.