Transmission Controlled Spark System: Description

The Transmission Controlled Spark (TCS) system is used to reduce HC and NOx emission by controlling distributor vacuum advance. Through the use of various switches and valves, this system allows vacuum advance only when the transmission is in 4th or 5th gear (manual transmission) or "D3" and "R" (automatic transmission). The system consists of a vacuum switching valve, top gear detecting switch, overdrive detecting switch (if equipped), thermal vacuum valve, vacuum delay valve (if equipped), and vacuum hose and wiring harness. See Figure.