Circuit Description

The EGR system recirculates exhaust gas through intake system to reduce combustion temperature and NOx emissions. The amount of EGR valve opening is regulated by the EGR vacuum modulator according to engine load. Vacuum source to valve is controlled by the Vacuum Switching Valve (VSV), which is controlled by ECM.

The EGR valve is closed (VSV on) under the following conditions:

• Engine is not warmed up.
• Vehicle under deceleration.
• Engine idling.
• High engine load.
• Engine speed more than 4400 RPM.

DTC is set when engine is warmed up, intake manifold absolute pressure is more than calculated valve by ECM while EGR system is on. DTC will also set if a misfire is detected during idling. Possible causes are:

• EGR valve stuck open.
• EGR Vacuum Switching Valve (VSV).
• EGR VSV open circuit.
• Manifold Absolute Pressure (MAP) sensor.
• ECM.