Circuit Description

Misfire is detected using Camshaft Position (CMP) and Crankshaft Position (CKP) sensors. When PCM senses CKP deceleration not associated with normal engine speed reduction, CMP is used to determine misfiring cylinder. PCM determines misfires on each cylinder and evaluates a random misfire and sets a DTC.

Conditions required to set code are:

• No VSS DTCs set.
• No CKP, CMP, ECT, MAF, MAP or TP sensor DTCs set.
• Engine speed 800-5500 RPM.
• System voltage 11-16 volts.
• ECT 20-248°F (-7-120°C).
• Throttle steady.
• PCM detects crankshaft RPM variation, indicating a misfire which could cause catalytic convertor damage or high emissions.