P1404
DTC P1404 EGR Valve Closed Pintle Position
Circuit Description
An Exhaust Gas Recirculation (EGR) system is used to lower Oxides of Nitrogen (NOx) emission levels caused by high combustion temperatures. It accomplishes this by feeding small amounts of exhaust gases back into the combustion chamber. When the air/fuel mixture is diluted with the exhaust gases, combustion temperatures are reduced.
A linear EGR valve is used on this system. The linear EGR valve is designed to accurately supply exhaust gases to the engine without the use of intake manifold vacuum. The valve controls exhaust flow going into the intake manifold from the exhaust manifold through an orifice with a VCM controlled pintle valve. The VCM commands EGR by applying a 12 volt duty cycle to the EGR valve feed control circuit. This can be monitored on a scan tool as Desired EGR position.
The VCM can monitor the pintle position with the EGR pintle position signal. This sensor uses a variable resistor with a 5 volt reference, a signal circuit and a ground. The signal circuit monitors changes in voltage on the variable resistor as the pintle moves.
Conditions for Running the DTC
- The ECT is between 80 - 120 °C (176 - 248 °F).
- The IAT is less than 100 °C (212 °F).
- The desired EGR position is greater than 15 percent.
Conditions for Setting the DTC
- The EGR pintle position voltage is 0.29 volt or greater with the EGR valve commanded closed.
- The above condition exists for more than 10 seconds.
Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The VCM records the operating conditions at the time the diagnostic fails. The Freeze Frame and Failure Records stores this information.
- The VCM stores a History DTC.
- The EGR Valve is disabled.
Conditions for Clearing the MIL/DTC
- The VCM turns OFF the MIL after 3 consecutive drive trips when the test has Run and Passed.
- A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22 °C (40 °F) from the startup coolant temperature and the engine coolant temperature is more than 70 °C (158 °F) during the same ignition cycle).
- Use the scan tool Clear Information function.
Diagnostic Aids
This diagnostic will detect the EGR pintle position not returning to the learned closed position due to foreign material lodged in the pintle seating area, or due to a defective EGR valve. The VCM will command the EGR valve fully open to attempt to clear the valve of any foreign material, although the vehicle must be at cruising speed for this to occur. If the third attempt to clear the valve is unsuccessful, the code P1404 will set.
An intermittent may be caused by any of the following conditions:
- A poor connection
- Rubbed through wire insulation
- A broken wire inside the insulation
Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Intermittents and Poor Connections Diagnosis.
If a repair is necessary, then refer to Wiring Repairs or Connector Repairs.
Steps 1 - 5:
Steps 6 - 11:
Steps 12 - 15:
Steps 16 - 17:
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
2. Commanding the EGR valve open and closed determines whether the EGR system can control the EGR valve accurately and if the EGR valve will return to the fully closed position.
4. When the EGR valve electrical connector is disconnected, the scan tool should display the Actual EGR Position as 0 percent. If it does not, the malfunction lies either in the EGR signal circuit or the VCM.
6. If the EGR valve 5.0 volt reference is shorted to voltage, the DMM will read battery voltage and additional DTCs may be set.
11. A poor electrical connection may have caused this DTC to set. Be sure to check the terminals for being backed out, improperly formed, damaged, and for poor tension.
15. The replacement VCM must be programmed and the Crankshaft Position System Variation Learn Procedure must be performed. Refer to VCM Replacement/Programming or CKP System Variation Learn Procedure.
16. Clearing the DTCs is a very important step for this diagnostic. The clearing function allows the EGR valve to relearn a new minimum pintle position as the old position was inaccurate due to the malfunction that caused the DTC. If the VCM sees an EGR command, the new minimum pintle position will not be learned.
17. If no malfunctions have been found at this point and no additional DTCs were set, refer to the Diagnostic Aids for additional checks and information.