Exhaust Gas Recirculation (EGR) System - General Information, Component Inspection and Replacement

General Information
To reduce nitrogen oxide emissions, the engine routes part of the exhaust gases into the intake manifold through the EGR valve. Mixing exhaust gas with the air-fuel mixture lowers combustion temperature.

The system consists of the EGR valve, the EGR valve position sensor, the powertrain control module (PCM), and a set of auxiliary information sensors. The PCM is programmed to set the optimal EGR valve opening for any engine operating condition. The position sensor continuously monitors the EGR valve opening and sends corresponding signals to the PCM. The PCM compares the sensor signal with the optimal value calculated from data supplied by the other sensors and, if necessary, adjusts the volume of exhaust gas entering the engine.
INSPECTION
PROCEDURE

1. To check the EGR valve position sensor, disconnect the wiring from the valve and check the sensor signal.
2. Next, check the EGR valve operation. Start the engine and warm it up to normal operating temperature (the cooling fan should come on). Then turn off the engine and disconnect the wiring from the EGR valve.

3. Using a jumper wire, connect the positive battery terminal to EGR valve terminal No. 4. Start the engine, then connect the negative battery terminal to valve terminal No. 6. Engine speed stability should be disrupted, up to complete engine stall. Otherwise, replace the EGR valve.

4. Further testing of the EGR system requires special tools and diagnostic equipment.

EGR Valve Component Replacement
PROCEDURE

1. Disconnect the wiring harness from the EGR valve position sensor.

2. Remove the two mounting nuts and remove the EGR valve.

3. Clean the mating surfaces of the valve and its adapter.
4. Replace the gasket and install the EGR valve in its original position. Tighten the mounting nuts securely.
5. Reconnect the wiring harness.