Component Location
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 one or more cylinders are misfiring.
DTC Description
If there happen misfires over the threshold value at #2 cylinder, ECM sets DTC P0302.
DTC Detecting Condition
Item | Detecting Condition | Possible Cause |
DTC Strategy | Engine roughness through crankshaft speed fluctuation
| Poor connection
Ignition system
Fuel system
Intake/exhaust air system
Ignition timing
Injector
|
Enable Conditions | Time after engine start > 25s
No CKP sensor error
Eng. load change = 41.2~200 %/cycle
Eng. speed change = 2105~4839 rpm/s
No rough road condition
No fuel cut off condition
Intake air temperature = -6?
|
Threshold Value | Misfire rate / cylinder > 10% of total misfire rate
|
Diagnostic Time | Continuous
|
MIL ON Condition | 3 driving cycle
|
Specification
Item | Specification |
Primary Coil Resistance (O) | 0.75O ± 15% [20 ? 68 ?] |