Positive Backpressure EGR Valve
A control valve, located in the EGR valve, acts as a vacuum regulator valve. The control valve regulates the amount of vacuum to EGR diaphragm chamber by bleeding vacuum to atmosphere during certain operating conditions.
When control valve receives a backpressure signal, through the hollow shaft of EGR valve, pressure on bottom of control valve closes control valve. When control valve closes, maximum vacuum signal is applied directly to EGR valve allowing exhaust gas recirculation.