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Diagnostic Trouble Code (DTC) P0406

EGR Pintle Position Sensor High Voltage




Features of the Circuit



  • By any chance if high combustion temperatures are created by oxides of nitrogen then An Exhaust Gas Re-circulation (EGR) system which is the chief feature of this system will be boosted to counter this.
  • This is done by supplying small amounts of exhaust gases back into the combustion chamber.
  • Combustion temperatures are minimized as soon as the air/ fuel mixture dilutes the exhaust gases.
  • The EGR valve has been specially designed to generate exhaust gases to the engine without using intake manifold vacuum.
  •  This valve regulates exhaust flow entering the intake manifold from the exhaust manifold through an orifice with an ECM controlled pintle.
  • The pintle position is monitored by the ECM using inputs from the Throttle Position (TP) and the Manifold Absolute Pressure (MAP) sensor.
  • This task over, the ECM then directs the EGR valve to operate as necessary by controlling an ignition signal through the ECM.
  • The ECM further monitors the results of its command through a feedback signal.
  • The desired EGR position can be checked with the help of a scan tool.
  • A voltage signal representing the EGR valve pintle position is sent to the ECM by a 5 volt reference and a ground to the EGR valve.
  • The scan tool can also be used here to note the feedback signal which is the actual position of the EGR pintle.
  • The correct EGR position should always be close to the commanded or Desired EGR position.
  • This Diagnostic Trouble Code (DTC) is capable of identifying an open or short circuit








Time for setting the DTC

Task boosted after DTC sets

When will DTC clear?

1) When EGR voltage is < 0.01V.


1) The Malfunction Indicator Lamp (MIL) will glow after three successive trips with a fail.

1) The MIL will turn off after four consecutive ignition cycles in which the diagnostic runs without a fault.


2) The ECM will begin to store conditions which were present when the DTC failed.


2) Disconnecting the ECM battery feed for 10 seconds


3) This information will be recorded in the Freeze Frame buffering Failure Records.


3) The scan tool can be used to remove all existing DTCs.



4) A history DTC will be stored.


4) A history DTC will clear after 40 consecutive warm-up cycles without a fault.





                                             DIAGNOSTICS TOOLS


  • Moisture related with exhaust systems might result in the EGR valve to freeze and malfunction in cold weather occasionally.
  •  This problem will be solved when the vehicle is taken to any warm shop for repairs and the affected part duly repaired.
  • The error in can be easily noted by comparing the Actual EGR and the desired EGR positions on a cold vehicle with a scan tool.
  • Note the Engine Coolant Temperature (ECT) and then check the Freeze Frame data to ensure that the DTC was set when the vehicle was cold.




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