Component Location
Description
1. General Description
Misfires can be caused by lack of combustion in a cylinder due to absence of spark, poor fuel metering, poor compression, or many other causes. Even a small number of misfires may result in excessive exhaust emissions due to the unburned mixture. Increased misfire rates cause damage to the catalytic converter. The ECM monitors the crankshaft speed variation to determine if any misfiring generated. The ECM identifies the specific cylinder in which the misfire has occurred and counts individual misfire events by monitoring changes in the crankshaft rotation for each cylinder. A random misfire indicates two or more cylinders are misfiring.
2. DTC Description
The ECM sets DTC P0301 if a misfire which result in damage to the catalyst or increase emissions happens in cylinder.
DTC Description
The ECM must monitor the engine for misfiring possibly caused by ignition coil defects or injector fails. If misfiring is detected, the ECM identify the cylinder(s) that has(have) misfired and calculate misfiring rate for a given duration. The DTC for Misfire (P0301 to 0304) is set as soon as misfiring rate exceed the limit which result in damage to the catalyst or increase emissions. The ECM stores individual DTC for the cylinder has more than 10% of total misfire rate. With more than two cylinders misfire detection, the ECM sets P0300.If the misfire rate is not extremely high, the MIL will be illuminated in the next driving cycle that diagnostic runs and fails.With extremely high misfire rate which has a danger of burning up the catalyst, the MIL blinks immediately.
DTC Detecting Condition
Item | Detecting Condition | Possible cause |
DTC Strategy | ? Crankshaft speed fiuctuation | ? Vacuum leak in air intake system ? CKPS circuit malfunction ? Ignition circuit malfunction ? Faulty ignition coil or pulg wire ? Spark plug malfunction ? Low compression due to blown head gasket, leaking valve or piston ring ? Low/high fuel pressure due to faulty ? pressure regulator,restricted fuel lines,plugged fuel filter or faulty fuel pump ? Fuel injector circuit malfunction ? Faulty fuel injector |
Threshold value | ? Misfire rate for FTP E/M thresh. > 5 % |
Enable Conditions | ? Engine speed 400-4520 rpm ? Engine load > Zero torq. ? Eng. load change < 7.7~357%/seg ? Eng. speed change < 1900~2600rpm/s ? No rough load < 0.3g ? 0 sec after engine start ? Intake air temperature > -7.5 degC |
Diagnostic Time | ? 1000 revs |
If any injectors, HO2S, ECTS, and MAP codes are present, do all repairs associated with those codes before proceeding this troubleshooting guide.
Specification
Ignition coil | Normal Parameter |
Resistance | Primary coil | 0.62? ± 10% |
Secondary coils | 7.0? ± 15% |
Plug wire | NO1 | 4.39~6.59 ? |
NO2 | 2.28~3.43 ? |
NO3 | 3.49~5.24 ? |
NO4 | 1.9 ~2.86 ? |
Schematic Diagram
Signal Waveform
This figures show the wave form of primary coil measured at terminal 2 of ignition coil at idle.Is ON named DWELL and its normal voltage is below 0.5V.
The voltage at point ? is power supply of IG coil and it should be battery voltage
The signal at ? is the duration when power TR in ECM is ON named DWELL and its normal voltage is below 0.5V.
In case over 0.5V |
Possible cause: Faulty power TR in ECM or poor ECM ground connection. |
The wave form at ? is surge voltage which occures at primary coil when power TR off and its normal voltage is over 320V.
In case when surge voltage is low |
Possible cause: Open circuit in power line or poor ground connection. |