Exhaust Gas Recirculation (EGR) Valve
The EGR valve in the differential pressure feedback EGR system is a conventional, vacuum-actuated valve. The valve increases or decreases the EGR flow. As vacuum applied to the EGR valve diaphragm overcomes the spring force, the valve begins to open. As the vacuum signal weakens, at 5.4 kPa (1.6 in-Hg) or less, the spring force closes the valve. The EGR valve is fully open at approximately 15 kPa (4.4 in-Hg).
Since EGR flow requirement varies greatly, providing repair specifications on flow rate is impractical. The on board diagnostic (OBD) system monitors the EGR valve function and triggers a DTC if the test criteria is not met. The EGR valve flow rate is not measured directly as part of the diagnostic procedures.