Circuit Description

PCM times the interval between each pulse of the CKP sensor and compares each time interval with the other 8 to determine when an excessive change in crankshaft speed has occurred.

This pulse is generated from a 4X reluctor wheel located on front of crankshaft. If crankshaft speed is less than an expected amount, PCM will increase amount of fuel needed to correct misfire. If amount of fuel exceeds the calibrated value, PCM will interpret this as a misfire and set the DTC. This misfire diagnostic is used only to identify a weak cylinder needing additional fuel.

DTC will set when the following conditions are present:

• ECT greater 132°F (56°C).
• Engine idling for total of 90 seconds.
• Fuel adjustment is greater than calibrated value (internal to PCM).
• Multiple engine misfires detected.