EC-12 EMISSION CONTROL SYSTEMS — Exhaust Gas Recirculation (EGR) System (7M-GE) EXHAUST GAS RECIRCULATION (EGR) SYSTEM (7M-GE) (1) EGR Port R Port EGR Vacuum Modulator EGR Valve VSV EC3033 (2) EGR Port R Port ECU VSV EGR Cooler EGR Vacuum Modulator EGR Valve EC3034 (3) EGR Port R Port ECU VSV EGR Cooler EGR Vacuum Modulator EGR Valve EC3035 To reduce NOx emissions, part of the exhaust gases are recirculated through the EGR valve to the intake manifold to lower the maximum combustion temperature. Coolant Temp. | *Engine RPM | VSV | Throttle Valve Opening Angle | Pressure in the EGR Valve Pressure Chamber | EGR Vacuum Modulator | EGR Valve | Exhaust Gas Below 57°C (135°F) | - | OPEN | - | - | - | CLOSED | Not recirculated Above 57°C (135°F) | Above 4,000 rpm | OPEN | - | - | - | CLOSED | Not recirculated | Below 4,000 rpm | CLOSED | Positioned below EGR port | (1) LOW | ** Pressure constantly alternating between low and high | OPENS passage to atmosphere CLOSES passage to atmosphere | CLOSED | Not recirculated Above 65°C (149°F) | | | Positioned between EGR port and R port | (2) HIGH | | | OPEN | Recirculated | | | Positioned above R port | (3) HIGH | *** | | OPEN | Recirculated (Increased) * Engine RPM control is for Calif. only. ** Pressure increase ——— Modulator closes ——— EGR valve opens ——— Pressure drops EGR valve close ——— Modulator opens ——— *** When the throttle valve is positioned above the R port, the EGR vacuum modulator will close the atmosphere passage and open the EGR valve to increase the EGR gas, even if the exhaust pressure is insufficiently low.