P1404

Circuit Description

This diagnostic test checks for a malfunction in the circuitry and hardware of the Linear EGR valve. This test is used to indicate a stuck open EGR valve. When the EGR valve desired position is 0 (closed) the current (closed) EGR pintle position is subtracted from the learned low EGR pintle position. If the difference between the two values is greater than 20 counts then a stuck open valve is indicated. When the open valve condition is indicated this test waits for the EGR to be opened enough so that a possible restriction (usually carbon deposits) could possibly clear. When the EGR valve desired position returns to 0 (closed) this test rechecks the difference between the closed and learned low pintle positions and if the significant difference is still there a timer is incremented. When the time limit has been reached a failure is indicated and this DTC is set.

Conditions for Running the DTC

^ Closed EGR pintle position is 0.
^ After an initial failure (open valve condition) is first indicated the desired EGR position has been cycled 120 counts or more.

Conditions for Setting the DTC

An open valve condition is monitored for at least 10 seconds, two times, this includes one time for the initial failure.

Action Taken When the DTC Sets

The PCM disables the Linear EGR valve for the ignition cycle.

^ The PCM will illuminate the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
^ The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records.

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 (current) 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 emission related 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.