Code P0401, EGR Flow Test Failure: Notes

PCM tests exhaust gas recirculation valve by momentarily commanding valve on while monitoring engine RPM. PCM will illuminate Malfunction Indicator Light (MIL) and store Code P0401 if expected drop is not seen for a calibrated number of tests. PCM will run EGR test when the following conditions are present.

• Codes P0122, P0123 or P0501 are not set.
• Brake has been applied.
• Engine coolant temperature is greater than 185°F (85°C).
• Throttle angle is less than one percent.
• Vehicle speed is greater than 25 MPH.
• Engine speed is 900-1100 RPM.
  NOTE: Test numbers refer to numbers on diagnostic chart.

1. Ensures EGR valve is allowing EGR flow and PCM is capable of controlling EGR valve.
2. Ensures control circuit is not shorted to ground.
3. Ensures control circuit is not open and that PCM quad-driver for circuit is properly functioning.