Electronic Control Module (ECM)

ECM receives signals from O2 sensor, thermosensor and engine speed sensor to adjust Air/fuel ratio to proper level.

Air/fuel ratio is judged to be rich when voltage produced by O2 sensor is higher than a set specified level. As a result, ECM signals duty solenoid to pass a greater quantity of air into carburetor. This additional air leans air/fuel mixture.

Air/fuel ratio is judged to be lean when voltage produced by O2 sensor is lower than a set specified level. As a result, ECM issues signals to duty solenoid to pass a less air into carburetor. The elimination of air enriches air/fuel mixture.