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 of occurred.

DTC will set when the following conditions are present:

• A number of high resolution pulses (internal to PCM) per every 8 cam reference pulses.