P0302

DTC P0302 - CYLINDER 2 MISFIRE DETECTED

OUTLINE OF DIAGNOSIS
Detect whether the misfire occurred or not. (Revolution fluctuation method)
Monitoring the misfire which influences exhaust deterioration (1.5 times of FTP) and catalyst damage is made obligatory by the law. Misfire affecting these two has three patterns below.
- Intermittent misfire (The same cylinder misfires in random, or different cylinders misfire in random.): FTP 1.5 times misfire
- Every time misfire (The same cylinder misfires every time.): FTP 1.5 times misfire, Catalyst damage misfire

The following detecting methods are adopted for these detection.
1. Intermittent misfire: FTP 1.5 times misfire
- 120 ° Interval Difference Method
- 360 ° Interval Difference Method (whole range)
- 720 ° Interval Difference Method (3,000 rpm or less)

2. Every time misfire: FTP 1.5 times misfire, Catalyst damage misfire
- 360 ° Interval Difference Method




ENABLE CONDITION

GENERAL DRIVING CYCLE
- The misfire is detected from idling to high engine revolution speed if the condition is matched.
- Perform the diagnosis continuously.

DIAGNOSTIC METHOD




When the misfire occurred, the engine speed is decreased and the crankshaft position speed will change. Calculate the interval difference value (diagnostic value) from crankshaft position speed by the following formula, and judge whether the misfire occurs or not comparing the calculated result with judgment value. Counting the number of misfire up, and if the misfire ratio is higher during 1000 rev. or 200 rev., judge NG for the corresponding cylinder.







As the figure, pick out a random cylinder as the standard and name it omg 0. And the former crankshaft position speed is named omg 1, the second former crankshaft position speed is named omg 2, the third is named omg 3, and the following is the same.




- 120 ° Interval Difference Method




- 360 ° Interval Difference Method




- 720 ° Interval Difference Method




- FTP 1.5 times misfire (Misfire occurrence level affecting exhaust gas)




- Catalyst damage misfire (Misfire occurrence level damaging catalyst)




- Map 1 Fault criteria threshold for misfire which would result in catalyst damage

DTC CLEAR CONDITION
- When the OK idling cycle was completed 40 times in a row
- When "Clear Memory" was performed

MALFUNCTION INDICATOR LIGHT CLEAR CONDITION
- When the OK driving cycle was completed 3 times in a row
- When "Clear Memory" was performed

FAIL SAFE
None

ECM OPERATING AT DTC SETTING
Memorize the freeze frame data. (For test mode $02)