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

Code is set when EGR gas temperature sensor value does not exceed 86°F (30°C) above ambient air temperature after vehicle is operated for 3-5 minutes at 50 MPH or more. Possible causes are:

• EGR valve malfunction.
• EGR gas temperature sensor open circuit.
• EGR step motor circuit.
• ECM malfunction.