Circuit Description

Optical sensor provides a pump cam signal to PCM by counting pulses on sensor disk located in injection pump. Pump cam is an important input by PCM for fuel control and timing. Test monitors number of crankshaft position pulses that have occurred since last cam pulse. Physical one-to-one correspondence between pump cam and crankshaft implies that if more crank pulses are detected than cam pulses, the cam pulses have been missed.

DTC will set when 8 consecutive cam pulses are missing, or an average of 8 cam pulses are missing.