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 controlled by a step motor located inside of EGR valve. The ECM operates the step motor in response to engine operating conditions.

The EGR valve is closed under the following conditions:

• Coolant temperature less than 129°F (54°C).
• Vehicle under deceleration.
• Light engine load.
• Engine speed more than 4000 RPM.
• Engine idling.
• Park/neutral position switch on.

DTC is set when EGR gas temperature sensor value is high during EGR cut-off when engine is cold, or if EGR valve is always open. Possible causes are:

• EGR valve stuck open.
• EGR stepper motor circuit.
• EGR temperature sensor short circuit.
• ECM.