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 set DTC. Conditions for setting DTC:

• No VSS DTCs set.
• No CKP, CMP, ECT, MAF, MAP or TP sensor DTCs set.
• Engine speed 525-5900 RPM.
• System voltage 9-18 volts.
• ECT 21-253°F (70-487°C).
• Throttle angle steady.
• PCM detects crankshaft RPM variation, indicating a misfire which could cause catalytic convertor damage or high emissions.