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Home >> GMC >> 1983 >> Forward Control 7.4 W, Standard >> Repair and Diagnosis >> Engine Performance >> System >> EGR System >> Operation >> EGR Thermal Vacuum Switch

EGR Thermal Vacuum Switch

EGR TVS, used on all models, closes to prevent EGR operations when engine coolant temperature is below 85°F (29°C). This improves cold engine driveability. When coolant temperature rises above 85°F (29°C), TVS opens to allow vacuum to be directed to EGR valve.