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 P0303 if a misfire which result in damage to the catalyst or increase emissions happens in cylinder.
DTC Detecting Condition
Item | Detecting Condition | Possible cause |
Monitoring Strategy | ? Crankshaft speed fiuctuation ? Multiple misfire | ? 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 fule 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 emission relevent > 1.25% |
? Misfire rate for catalyst damage > 7 ~ 25%(Catalyst temp.>950?(1742?) |
Enable Conditions | ? Engine speed 520~6800 |
? Engine Load (rl) > 12%~max ? Engine load (rl) change < 85~292%/seg ? Engine speed change < 2860~3569rpm/s ? Rough road < 0.3g at 30Km/h ? Time from engine start 0 sec ? Engine Torque > zero torque ? Intake air temperature > -30?(-22?) |
? Same as above |
Diagnostic Time | ? 1000 revs Continuous |
? 200 revs Continuous |
MIL on condition | ? 2 driving cycle |
? Immediatey |
If any injectors, HO2S, ECTS, and MAP codes are present, do all repairs associated with those codes before proceeding this troubleshooting guide.
Specification
Primary coil : 0.87? ± 10% |
Secondary coils : 13.0? ± 15% |
Plug wire |
NO1 : 4.39~6.59 |
NO2 : 2.28~3.43 |
NO3 : 3.49~5.24 |
NO4 : 1.9 ~2.84 ? |
Schematic Diagram
Signal Waveform
This figures show the waveform of primary coil measured at terminal 1 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 waveform 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. |
Signal Waveform
This figures show the waveform of primary coil measured at terminal 2 of ignition coil at idle.
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 waveform 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. |
Is Sensor Switching Properly?
In case there is no symptom and wrong data but DTC is shown |
The problem may be intermittent so slightly shake the connector and harness vertically and horizontally to check if there is any data changes |
If the data changes normally, the problem was intermittent so erase DTC and verify the same DTC reoccure. Go to "Terminal and Connector inspection" procedure. |
In case there is symptom and wrong data with DTC |
Check open,short or connector’s connection for HO2S. |
Check the deterioration of Ignition coil performance. Go to "Circuit Inspection" procedure. |