Oxygen Sensor

Oxygen sensor signals ECU to change duty cycle (dwell) of frequency valve based on amount of oxygen in exhaust gas. Deceleration switch forces oxygen sensor system to shut down for 1/2 second time interval when throttle is closed very rapidly.

This avoids extreme leaning of mixture by oxygen sensor system, which could cause stalling of engine. ECU has barometric cell which gives additional control to duty cycle based on altitude. System must be adjusted to correct duty cycle for local elevation. When set correctly, system will function at all altitudes.