Operation

Operation:

Description:

EGR System Operation

The linear EGR valve is designed to accurately supply EGR to an engine independent of intake manifold vacuum. The valve controls EGR flow from the exhaust to the intake manifold through an orifice with a PCM controlled pintle. During operation, the PCM controls pintle position by monitoring the pintle position feedback signal. The feedback signal can be monitored with a scan tool as ACTUAL EGR POS. ACTUAL EGR POS should always be near the commanded EGR position (DESIRED EGR POS). The PCM uses information from the following sensors to control the pintle position:
^ Engine Coolant Temperature (ECT) sensor.
^ Throttle Position (TP) sensor.
^ Mass Air Flow (MAF).

The linear EGR valve is usually activated under the following conditions:
^ Warm engine operation
^ Above idle speed

Diagnosis

Too much EGR flow at idle, cruise, or cold operation may cause any of the following conditions to occur:
^ Engine stalls after cold start.
^ Engine stalls during closed throttle conditions.
^ Vehicle surges during cruise.
^ Rough idle.
^ DTC P0300 (misfire detected).

Too little or no EGR flow may allow combustion temperatures to get too high. This could cause the following symptoms:
^ Spark knock (detonation).
^ Engine overheating.
^ Emission test failure.
^ DTC P0401.
^ Poor fuel economy.

EGR flow diagnosis is included in the DTC P0401 diagnostic table. Pintle position error diagnosis is covered in DTC P1406. If EGR diagnostic trouble codes P0401 and/or P1406 are encountered, go to the DTC tables for diagnosis.