The exhaust gas recirculation (EGR) system on the Toyota Corolla is located near the rear of the engine, on the firewall side. It consists of the EGR valve, EGR vacuum modulator and the thermal vacuum switching valve (TVSV). The system reduces oxides of nitrogen by recirculating some of the exhaust gases through the EGR valve and intake manifold, into the cylinders. This also reduces combustion temperatures. A malfunctioning EGR could cause a misfire in the engine. If you have an EGR code on the code scanner, it could be for insufficient or excessive flow.
Loosen the hose clamps on the vacuum lines attached to the EGR valve, using the screwdriver.
Pull the hoses off the valve. Remove the valve, using the appropriate socket.
Position the new gasket on the intake manifold. Install the new EGR valve and tighten the bolts firmly. Reattach the vacuum hoses and tighten the clamps.
Label the three vacuum hoses on the vacuum modulator with the tape and marker: Port P is the single port on one side of the modulator. Label the other hoses Q and R (with Q being the top hose).
Plug ports P and R, using your fingers. Blow air into the port Q. The air should pass freely through the sides of the air filter.
Start the engine and hold the rpm at 2,000. Repeat the air test. There should be a strong resistance to air flow. If the modulator fails either test, replace it. Install the new modulator and plug the vacuum lines into their respective ports.
