The exhaust gas recirculation (EGR) valve consists of a pintle valve which moves by the use of an internal solenoid and an internal position sensor (potentiometer) used to determine pintle valve position. The powertrain control module (PCM) controls the solenoid by supplying it ignition voltage whenever exhaust gas needs to be recirculated into the intake manifold. The PCM monitors the EGR solenoid and position sensor circuits for correct voltage levels at certain times. The PCM also monitors the position of the sensor in relation to its duty cycle (commanded On-time). DTC P0404 sets when the actual EGR position from the position sensor is less than or greater than the commanded EGR position based on the duty cycle of the solenoid.

The DTC P0404 will set if commanded EGR position is less than 80 percent and actual EGR position is more than 10 percent above or below commanded EGR position for 10 seconds.

OR

Commanded EGR position is greater than 80 percent and actual EGR position is more than 24 percent above or below commanded EGR position for 10 seconds.

The above conditions must exist for 10 seconds with ignition voltage greater than 11 volts.

DTC P0404 diagnostic runs continuously once the above conditions have been met.

Important: The actual and commanded EGR position readings are only valid when EGR solenoid is commanded by PCM, no scan tool.

DTC P0404 is a type B DTC.

If DTC P0403, P0405, P1403 or P1404 is set, diagnose that DTC first. A diagnosed EGR solenoid or EGR position sensor fault will cause this DTC to set.

Use a scan tool to command EGR SOLENOID ON while monitoring EGR SENSOR. The values for EGR SENSOR at a commanded state of 0 percent and 70 percent should fall within these ranges:

Debris is most likely the cause of this DTC. If EGR SENSOR values do not fall within these ranges, remove EGR valve and move pintle valve by hand to remove debris. Clean any debris that may be in the EGR port and check for corrosion in EGR harness connector. Retest EGR and replace if test fails again.