Circuit Description

The optical sensor provides a high resolution signal to the powertrain control module (PCM) by counting pulses on the sensor disk located in the injection pump. This test monitors the number of high resolution pulses which have been missed. The test is based on a comparison between the number of pulses that were detected since the last pump cam pulse and the number of pulses that should have occurred. There are approximately 64 high resolution pulses for every cam pulse.