EGR Valve: Description and Operation

Electric Exhaust Gas Recirculation (EEGR) Valve

EEGR Motor/Valve Assembly:

Depending on the application, the EEGR valve is a water cooled or an air cooled motor/valve assembly. The motor is commanded to move in 52 discrete steps as it acts directly on the EEGR valve. The position of the valve determines the rate of EGR. The built-in spring works to close the valve (against the motor opening force).

Exhaust Gas Recirculation (EGR) System Module (ESM)

ESM:

The ESM is an integrated differential pressure feedback EGR system that functions in the same manner as a conventional differential pressure feedback EGR system. The various system components have been integrated into a single component called the ESM. The flange of the valve portion of the ESM bolts directly to the intake manifold with a metal gasket that forms the metering orifice. This arrangement increases system reliability, response time, and system precision. By relocating the EGR orifice from the exhaust to the intake side of the EGR valve, the downstream pressure signal measures manifold absolute pressure (MAP). This MAP signal is used for EGR correction and inferred barometric pressure (BARO) at key on. The system provides the powertrain control module (PCM) with a differential pressure feedback EGR signal, identical to a traditional differential pressure feedback EGR system.

Exhaust Gas Recirculation (EGR) Valve

Typical EGR Valve:

EGR Flowrate:

The EGR valve in the differential pressure feedback EGR system is a conventional, vacuum-actuated. The valve increases or decreases the flow of EGR. 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 about 15 kPa (4.5 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 diagnostic trouble code (DTC) if the test criteria is not met. The EGR valve flow rate is not measured directly as part of the diagnostic procedures.