P0404

Circuit Description

This diagnostic test checks for a malfunction in the circuitry and hardware of the Linear EGR valve. The ability of the PCM to control the EGR valve is checked with this test. When the PCM commands the EGR valve to a desired position and changes that position less than a calibratable amount, this test then checks the EGR pintle position error. If the pintle position error, which is the difference between the desired pintle position and the actual pintle position, is too great then this DTC is set.

Conditions for Running the DTC

^ Engine vacuum is greater than 49.7 kPa.
^ Transmission temperature is greater than 89.7°C (193.4°F).
^ The maximum change in desired pintle position during this test is less than 25 counts if the Ignition voltage is more than 12 volts or 10 counts if the Ignition voltage is less than 12 volts.

Conditions for Setting the DTC

^ Ignition voltage 12 volts or less.
The linear EGR pintle position error is greater than 75 counts.
^ Ignition voltage more than 12 volts.
The linear EGR pintle position error is greater than 25 counts.

Action Taken When the DTC Sets

The PCM disables the EGR solenoid for the ignition cycle.

^ The PCM will illuminate the Malfunction Indicator Lamp (MIL) after two consecutive drive trips that the diagnostic runs and fails.
^ The PCM will record operating conditions at the time the DTC sets. This information will be stored in the Freeze Frame and Failure Records.
^ A first failure of this DTC will store in Last Test Failed but not History.

Conditions for Clearing the MIL/DTC

^ The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail.
^ A Last Test Failed DTC will clear when the diagnostic runs and does not fail.
^ A History DTC will clear after forty consecutive warm-up cycles with no failures of any diagnostic test.
^ Use a scan tool to clear DTCs.
^ Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended.

Test Description

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

2. Checking if EGR valve feedback is valid with EGR OFF.
3. With the EGR valve OFF, the feedback should be 1.0 volt or less.
4. At 50% EGR commanded ON, compare the Actual EGR pintle position to the Commanded EGR pintle position. If the Actual EGR pintle position is 0, the fault is in the EGR control circuit, the EGR valve or the PCM. If the Actual EGR pintle position varies above and below the Commanded EGR pintle position the fault is in the EGR valve ignition feed (C2-34) or the PCM.
5. With the EGR valve commanded on full, the EGR pintle position should be above 4.0 volts.
6. The Freeze Frame or Failure Rec., EGR pintle position, display can help determine the root cause even if the problem cannot be reproduced. If a low pintle position is recorded in the snapshot, that means a low feedback circuit voltage caused the DTC to set.
7. The Freeze Frame or Failure Rec., EGR pintle position, display can help determine the root cause even if the problem cannot be reproduced. If a high pintle position is recorded in the snapshot, that means a high feedback circuit voltage, possibly open, caused the DTC to set. If an intermediate pintle position is recorded in the snapshot, that means the DTC was probably set because the PCM could not control the EGR solenoid either due to intermittents in the solenoid or a sticky EGR valve.
16. If audible valve movement is heard when disconnecting the EGR connector check the EGR Valve Control circuit for a short to ground.
32. A high voltage reading on the 5 volt reference circuit could be caused by a short to voltage on another 5 volt reference circuit, some 5V Ref. circuits are shared inside the PCM, or battery voltage bleeding onto the 5 volt reference circuit as in a defective Linear EGR Valve.