P1404

Schematic:

CIRCUIT DESCRIPTION
This diagnostic tests for an EGR valve that is stuck open. The PCM tests for a stuck open valve when the desired EGR position is at 0 percent. The PCM determines that the EGR valve is stuck open if the actual EGR position and the learned closed EGR position vary by more than a predetermined value. The PCM attempts to clear any obstructions from the valve. To clear the obstruction the PCM waits for the EGR desired position to be greater than 20 percent. Once the desired EGR position is more than 20 percent the PCM commands the EGR valve to 100 percent then back to 0 percent. The PCM does this three times. The PCM retests for a stuck EGR valve when the desired EGR position returns to 0 percent. A failure counter increments if the stuck EGR valve condition is still present. This DTC sets when the counter reaches a predetermined value.

CONDITIONS FOR RUNNING THE DTC
The ignition voltage is more than 11.7 volts.

CONDITIONS FOR SETTING THE DTC
The actual closed EGR pintle position voltage is 0.29 volts more than the desired closed EGR pintle position voltage

ACTION TAKEN WHEN THE DTC SETS
^ The PCM illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
^ The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Freeze Frame and/or the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM turns the Malfunction Indicator Lamp (MIL) OFF after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A last test failed (current DTC) clears when the diagnostic runs and does not fail.
^ A History DTC clears after 40 consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures.
^ Use a scan tool in order to clear the MIL/DTC.

DIAGNOSTIC AIDS

IMPORTANT:
^ Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM.
^ For any test that requires probing the PCM or a component harness connector, use the J 35616-A connector test adapter kit. Using this kit prevents damage to the harness/component terminals. Refer to Using Connector Test Adapters in Diagrams.

For an intermittent condition, refer to Symptoms. Symptom Related Diagnostic Procedures

TEST DESCRIPTION

Steps 1 - 6:

Steps 7 - 14:

Steps 15 - 19:

The numbers below refer to the step numbers on the diagnostic table.
2. If DTC P1635 sets at the same time, this indicates that the 5 volt reference circuit is either shorted to ground or shorted to a voltage. The 5 volt reference circuit is internally connected within the PCM.
3. This step tests for open EGR valve when the valve should be closed.
6. Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicated the DTC, the information included in the Freeze Frame and/or Failure Records data can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed.
5. This step tests for an EGR pintle position voltage that is out of range. The EGR pintle position voltage should be between 0.14 and 1.07 volts at idle.
8. This tests whether the ground circuit is available to the EGR valve. Inspect for poor electrical connections at the EGR valve.