EGR Valve: Description and 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 POSITION should always be near the commanded EGR position (DESIRED EGR POS.). If a problem with the EGR system will not allow the PCM to control pintle position properly, DTC P1406 should set. The PCM also tests for EGR flow; if incorrect flow is detected, DTC P0401 should set. If DTCs P0401 and/or P1406 are encountered, refer to the applicable DTC table.

The linear EGR valve is usually activated under the following conditions:

^ Warm engine operation.

^ Above idle speed.

The PCM monitors EGR actual position and adjusts pintle position accordingly. 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).