Circuit Description

Optical sensor provides a high resolution signal to PCM by counting pulses on sensor disk located in injection pump. High resolution is an important input by PCM for fuel control and timing. Test monitors number of high resolution pulses that have been missed (not detected). Number of pulses detected since last pump cam pulse is compared to number of pulses that should have occurred.

DTC will set when a number of high resolution pulses (internal to PCM) are missing per every 8 cam reference pulses.