P0404

Diagnostic Chart:

Wiring Diagram:

Circuit Description

The 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 valve. 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/Barometric pressure (BARO) sensor, the PCM makes minor adjustments to correct.


Conditions for Setting the DTC

^ The PCM performs this DTC diagnostic continuously.

^ The DTCs P0405, P0406, P0102 and P0103 are not set.

^ The EGR Vent Solenoid ON.

^ The difference between ambient air pressure and EGR pressure is less than 15 kPa.

^ All diagnostic set conditions met for 2 seconds


Action Taken When the DTC Sets

^ The PCM will shut down the EGR.

^ The PCM illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive drive trip that the diagnostic runs and fails.

^ The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the Failure Records will store this information. If the diagnostic reports a failure on the second consecutive drive trip, the Freeze Frame records the operating conditions at the time of failure and updates the Failure Records.

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.

^ Use of a Scan Tool


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.

To run the diagnostic test the engine must be at operating temperature, vehicle in drive at idle for approximately 1 minute, the with vehicle in park hold engine rpm steady between 1500 and 2100 rpm for 30 seconds. If the diagnostic test fails to run, vehicle must be driven.

The Adaptive Learn Matrix (ALM) is used to adjust the EGR vacuum control based on Mass Air Flow (MAF). The ALM may change as a result of back pressure increases over the lite of the vehicle or other engine system variations. The ALM is made up of sixteen cells (numbered from zero to fifteen) in which each cell covers a range of engine speed (RPM) and load (mm3).


Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

3. This step checks vacuum to the EGR valve control pressure/BARO sensor.