Tach Pulse (Rpm Reference) Signal
WARNING: This page is about a different car, the 1996 Pontiac Firebird and 1996 Chevrolet Camaro. However, it is still accessible from the selected car via links, so may be relevant.
Connect scan tool to DLC. Scan low and high resolution reference pulses. Both high and low pulses should be present when engine is cranking or running. If low resolution pulse is not present, engine will not start and PCM will set a Diagnostic Trouble Code (DTC) in memory. If high resolution pulse is not present, vehicle will still run; however, PCM will set a DTC in memory. For circuit and terminal reference, see appropriate schematic in NO START - ENGINE CRANKS OKAY in this article or TESTS W/CODES article.