Diagnostic Trouble Code (DTC) P0406

Exhaust Gas Recirculation Pintle Position High Voltage

 

 

Circuit Features

 

 

 

  • 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 which is linear 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 required EGR position can be checked with the help of a scan tool.
  • By sending a 5 volt reference and a ground to the EGR valve, a voltage signal representing the EGR valve pintle position is sent to the ECM.
  • 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 designed to identify a short circuit.

 

  

 

Time for setting the DTC

Task boosted after DTC sets

When will DTC clear?

DTC  sets when

1) EGR position signal > 98%

1) The Malfunction Indicator Lamp (MIL) will be seen to glow after three repetitive and failed cycles.

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

2)  Ignition voltage ranges around 11.7 and 16 volts.

 

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

 

2) De-linking the ECM battery feed for 10 seconds.

3) Fail condition persists for a time beyond 10 seconds.

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

 

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

 

4) Engine keeps running.

4) A history DTC will be stored.

 

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

 

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5) EGR is not enabled.

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Diagnostic Tools

 

  • Water vapor related to exhaust systems may freeze the EGR valve and make it stick in cold weather occasionally.
  • The valve will be made to get warm and normalize once it is brought to a repair shop.
  • The flaw can be detected by observing the Actual EGR and Desired EGR Positions on a cold vehicle taking a scan tool.
  • By observing the freeze frame data, the time when the DTC had set can be verified.

 

 

 

Test Description

 

 

Number(s) below indicate the step number(s) on the Diagnostic Table that follows.

  1.  The On-Board Diagnostic (EOBD) System Check is designed to assist the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This automatically creates an electronic copy of the data taken at the time the malfunction occurred. For future use this information is then stored on the scan tool.

 

2.In this step, controlling the EGR valve open informs if the EGR system can regulate the EGR valve desirably and also if any fault is present.

3.If the EGR valve 5 volt reference is shorted to ground, the digital voltmeter (DVM) will read no voltage and additional DTCs may be set and the engine performance will be poor. When this circuit is open, only a DTC P0405 will be set.

4.In this step a jumpering is done. Jumpering the 5 volt reference circuit to the signal circuit examines the signal circuit and the ECM. Ideally the scan tool must show the Actual EGR Position as 100% if the signal circuit and ECM are not malfunctioning.


6.A problem may remain latent within the terminals which would not be visible while examining type testing even if the ECM and circuitry acted correctly in the previous step. Remember to check the terminals and see that they are not being backed out, inaccurately formed or damaged, or if there is any tension.


10.   All circuits to the EGR valve must be functioning at this juncture. Since the fault lies internally in the EGR valve so it must be changed. Ensure that all gasket material is taken away from the EGR mounting surface. Presence of very a small amount of material may set DTC P0401.

12.   The substitution of the ECM needs to be reprogrammed. You may consult the latest Techline procedure for ECM reprogramming.

13.   Examine the terminals and see that they are not being backed out, inaccurately formed or damaged, and have no poor tension.


14.   Removing DTCs is very essential in this step. The clearing function enables the EGR valve to relearn a new pintle position as the old pintle position was faulty on account of the failure that caused the DTC. The DTC needs to be removed keeping the ignition ON and the engine OFF or at idle. If the ECM finds any EGR command, then the new pintle will not be known.


15.   If you do not find any malfunction at this point and also no additional DTCs set, then you need to consullt “Diagnostic Aids" in this section for additional checks and information.