Circuit Description

If PCM determines that engine is misfiring, but can not determine which cylinder is causing misfire, DTC P0300 will be set. This is normally the case when an ignition coil malfunctions because it fires more than one cylinder.

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°F-248°F (7°C-120°C).
• Throttle angle is steady.
• 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.