If the PCM detects that engine speed variation indicates a misfire sufficient to cause three-way catalyst converter damage or emissions level to exceed standard value, the PCM sets DTC P0304. If the misfire rate is high enough to damage the catalyst, the MIL will flash to alert the vehicle operator.
Item | Detecting Condition | Possible Cause | |
DTC Strategy |
•
Calculation of engine roughness | 1. Faulty spark plugs or Ignition coil 2. Incorrect valve timing 3. Uneven compression 4. Air leakage 5. Improper Fuel pressure or dirty fuel. 6. Blocked/Leaking injectors 7. Leakage between cooling system and cylinder | |
Enable Conditions |
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Engine load ratio : 14~64%
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470< Engine speed(rpm) <6700
•
Mass air flow gradient/sec. : 12~60%
•
Throttle gradient/sec. :58.6~1265.6%
•
Coolant temperature >20℃(68℉) if start temp. <-7℃(19℉)
•
No relevant failure
•
Fuel cut-off not active
•
11V< Battery voltage <16V | ||
Threshold Value | Case1 |
•
Misfire ratio :10 ~ 50% within 200 rev. | |
Case2 |
•
Misfire ratio :2.0% within 1,000 rev. | ||
Diagnosis Time | Case1 |
•
200 rev | |
Case2 |
•
1000 rev. | ||
MIL On Condition | Case1 |
•
Immediate | |
Case2 |
•
2 Drive Cycles | ||
