P0404

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) operates a solenoid to control the EGR valve. This solenoid is normally open. By providing a ground path the PCM energizes the solenoid which then allows vacuum to pass to the EGR. During normal operation, the PCM compares its desired EGR signal with the EGR pressure signal and makes corrections in the duty cycle accordingly. If there is a difference in the PCM command and what is at the EGR valve sensed by the EGR control pressure/BARO sensor, the PCM makes minor adjustments to correct.

CONDITIONS FOR SETTING THE DTC
- DTCs P0405 or P0406 are not stored.
- ENGINE SPEED greater than 506 rpm.
- (Desired EGR pressure) - (Measured EGR pressure) > 50 kPa.
- Above conditions persist for at least 25.5 seconds.

ACTION TAKEN WHEN THE DTC SETS
The PCM will shut down the EGR.

CONDITIONS FOR CLEARING THE MIL/DTC
- The PCM will turn the MIL off after three consecutive trips without a fault condition.
- A History DTC will clear when forty consecutive warm-up cycles that the diagnostic does not fail (coolant temperature has risen 5°C (40°F) from start up coolant temperature and engine coolant temperature exceeds 71°C (160°F) that same ignition cycle.

DIAGNOSTIC AIDS
A vacuum leak or a pinched vacuum will cause a DTC P0404. Check all vacuum lines and components connected to the hoses for leaks or sharp bends or deformities. Check vacuum source to EGR solenoid assembly. Also check for small leak in EGR valve, and proper vacuum line routing.

TEST DESCRIPTION
Number(s) below refer to the Step number(s) on the Diagnostic Table.

3. This step checks vacuum to the EGR valve.
4. This step checks for a faulty EGR vent solenoid.
5. This step checks for a good vacuum source. The vacuum gauge will fluctuate at the approximate specified value.