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.
Light engine load.
Engine racing.

DTC is set when after engine is warmed up, intake manifold absolute pressure is larger than value calculated by ECM while EGR system is on. Possible causes are:

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

NOTE: If DTCs P0105, P0106 and P0402 are output together, perform DTC P0105 circuit test first. If DTCs P0401 and P0402 are output together, perform P0402 circuit test first.