P0406

DTC P0406

Circuit Description

The powertrain control module (PCM) and the alternative fuels ECM monitor the exhaust gas recirculation (EGR) valve pintle position. If the alternative fuels ECM detects an excessively high EGR valve position signal voltage, DTC P0406 will set.


Conditions for Running the DTC

The vehicle is operating on CNG.


Conditions for Setting the DTC

* The EGR valve position signal voltage is more than 4.9 volts.
* The condition exists for more than 5 seconds.



Action Taken When the DTC Sets

* The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
* The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.



Conditions for Clearing the MIL/DTC

* The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
* A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
* A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
* Clear the MIL and the DTC with a scan tool.



Test Description

The number below refers to the step number on the diagnostic table.
2. This step verifies that the condition is present.
4. This step determines if the signal circuit of the EGR valve is shorted to a voltage.
5. This step tests the 5 volt reference circuit of the EGR valve. If the DMM displays above 5 volts, test the circuit for a short to voltage.
7. This step tests the low reference circuit of the EGR valve position sensor. If the test lamp does not illuminate, test the circuit for an open.
8. This step verifies that the PCM is not the cause of the condition.