Code P0401, EGR Flow Test Failure: Notes
WARNING: This page is about a different car, the 1995 Pontiac Trans Sport, 1995 Oldsmobile Silhouette, and 1995 Chevrolet Lumina APV. However, it is still accessible from the selected car via links, so may be relevant.
Control module tests exhaust gas recirculation valve by momentarily commanding valve on while monitoring engine RPM. Control module will illuminate Malfunction Indicator Light (MIL) and store Code P0401 if expected drop is not seen for a calibrated number of tests.
NOTE:
Test numbers refer to numbers on diagnostic chart.
- Ensures EGR valve is allowing EGR flow and control module is capable of controlling EGR valve.
- Ensures control circuit is not shorted to ground.
- Ensures control circuit is not open and that control module quad-driver for circuit is properly functioning.