(3X) Reference PCM Input

The PCM uses this signal from the electronic ignition module in order to calculate the engine speed and the crankshaft position. The PCM compares pulses on this circuit to the reference low CKT 453. The PCM also uses the pulses on this circuit to initiate fuel injector pulses. If the PCM receives no pulses on this circuit, no fuel injection pulses occur and the engine will not run.