Distributor Reference Signal

Ignition System Circuit:

Purpose:
The ignition system provides the ECM with high and low resolution pulses. These pulses are interpreted by the ECM as timing references, crankshaft position, firing order and RPM.

Operation:
One CPS senses 360 equally-spaced slots in the signal disk to provide 360 "ON" signals and 360 "OFF" signals per camshaft revolution. This provides the ECM with high resolution pulses. The ECM interprets high resolution pulses as detailed reference signals and crankshaft position information.

The other optical sensor senses 8 disk slots of variable length, providing low resolution pulses to the ECM. Low resolution pulses reflect to the ECM which spark plug is being fired.

The ECM can determine if one of the timing inputs is not being received by comparing the two inputs. Reference signals toggle between 0 and 5 volts as the camshaft turns.

Location:
The distributor is mounted directly to the camshaft next to the water pump. The distributor contains one signal disk and two optical Camshaft Position Sensors (CPS) that provide signals to the ECM for timing control.