Circuit Description

If PCM determines engine is misfiring and can determine actual cylinder that is misfiring, DTC P0301-P0304 will set. This is normally caused by failed fuel injector, spark plug or spark plug wire.

Conditions required to set DTC are:

• No related DTCs set.
• Engine speed is 600-6250 RPM.
• System voltage is 11-16 volts.
• ECT value is between 20-248°F (-7-120°C).
• Throttle angle is steady and changes less than 2.73 percent per second.
• TP sensor reads less than 3.125 percent.
• Vehicle speed is greater than 20 MPH.
• Engine under a load.
• PCM detects crankshaft RPM variation, indicating a misfire which could cause catalytic convertor damage or high emissions.