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 misfire DTC. If the misfire rate is high enough to damage the catalyst, the MIL will flash to alert the vehicle operator. With a more than two cylinder misfire detection, the PCM/ECM sets P0300.
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%
•
500< Engine speed(rpm) <6700
•
Mass air flow gradient/sec. :12~60%
•
Throttle gradient/sec. : 0.5~10.5%
•
Coolant temperature >20℃(68℉) if start temp. <-7℃(19℉)
•
No relevant failure
•
Fuel cut-off not active
•
11V< Battery voltage <16V | |
Threshold Value |
•
Misfire detected on 2 or more cylinders | |
Diagnostic Time |
•
Continuous | |
Mil On Condition |
•
Immediate (Misfire enough to damage the catalyst)
•
2 Driving Cycles (Misfire breaking the emission regulation) |
