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 P0303. 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 |
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Calculation of Engine Roughness. | 1. Poor Connector Connection 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 System | |
Enable Conditions |
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Engine load ratio more than 14 to 64% depends on engine speed and ECT.
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Engine speed higher than 470 RPM and lower than 6700 RPM.
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Ambient Pressure Model more than 10.9 psi(0.75bar).
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Engine load ratio gradient less than 12 to 60%/s.
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Throttle gradient more than 58.6 to 1265.6 %/s.
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Engine Coolant Temperature(ECT) higher than 68℉(20℃) if start Temp. is lower than 19.4℉(-7℃).
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Battery voltage higher than 11V and lowre than 16V.
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Fuel cut off not active.
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No rough load condition : - Moving mean value of wheel speed signal gradient more than 13 ~25‰. | ||
Threshold Value | Case1 |
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Misfire ratio more than 1.8% within 1000 rev. | |
Case2 |
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Misfire ratio more than 10~50% within in 200 rev. | ||
Diagnostic Time | Case1 |
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1000 rev. or 4*1000 rev. | |
Case2 |
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200 rev. or 3*200 rev. | ||
MIL ON Condition | Case1 |
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2 Driving Cycles. | |
Case2 |
•
1 Driving Cycle. | ||
