Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. 2. This step verifies that the malfunction is present.
2. 3. If DTC P0404 will only set under certain conditions, the malfunction may be intermittent. Refer to Diagnostic Aids. If an intermittent wiring problem is not present, test for a faulty connection at the PCM or the EGR valve. If the connections are OK and DTC P0404 continues to set, replace the EGR valve.
3. 6. When using the scan tool to increment the EGR valve, increment the valve to 10 percent then to 0 percent. Repeat this process to see if the test lamp turns ON then OFF. If the test lamp does not turn OFF when the EGR valve is commanded to 0 percent, the EGR solenoid high control circuit is shorted to voltage.
4. 7. When using the scan tool to increment the EGR valve, increment the valve to 10 percent then to 0 percent. Repeat this process to see if the test lamp turns ON then OFF. If the test lamp does not turn OFF when the EGR valve is commanded to 0 percent, the EGR solenoid high control circuit is shorted to voltage. If the test lamp does not turn ON when the EGR valve is commanded to 10 percent, the EGR solenoid high control is open or is shorted to ground.

Fig 1: DTC P0404 (1 Of 3)

Courtesy of GENERAL MOTORS CORP.

Fig 2: DTC P0404 (2 Of 3)

Courtesy of GENERAL MOTORS CORP.

Fig 3: DTC P0404 (3 Of 3)

Courtesy of GENERAL MOTORS CORP.