1. Ignition Coil
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.
If there happen misfires over the threshold value at #1 cylinder, ECM sets DTC P0301.
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
No rough road condition
No fuel cut off condition
Threshold Value
Misfire rate / cylinder > 10% of total misfire rate (emission threshold)
Misfire rate / cylinder > 25% of total misfire rate (catalyst damage threshold)
Diagnostic Time
Continuous
MIL ON Condition
3 driving cycle or Immediately (Blink)
Specification
Primary Coil Resistance (O)
0.75O ± 15% [20 ? 68 ?]