DECEL Throttle Modulator: Description

The decel throttle modulator system, used on some Heavy Duty emissions models, keeps the throttle valves open slightly during deceleration to help reduce emissions. System consists of a speed sensor, solenoid vacuum valve, throttle modulator on throttle linkage, ported vacuum switch, and electrical wiring and vacuum hoses. The system is electrically connected to the "B+" terminal of the ignition switch and to the "+" terminal of ignition coil. See Figure.