If the PCM/ECM 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/ECM 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 |
•
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 |
•
Engine load ratio : 14~64%
•
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 | ||
