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the code is for the egr valve operation. in most cases, there is carbon that builds up on the pindle of the valve and will not allow the valve to seat correctly. removing the valve and inspecting will confirm. it will be obvious. if that is ok, make sure the passages are clear and you will need to replace the valve.
Circuit DescriptionAn exhaust gas recirculation (EGR) system is used in order to lower oxides of nitrogen (NOx) emission levels caused by high combustion temperatures. The EGR 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 in order 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 control module controlled pintle valve. The control module commands the EGR by applying a 12 volt duty cycle to the EGR valve. This can be monitored on a scan tool as desired EGR position.The control module 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.The VCM will set a DTC P0404 if it detects a large enough difference between desired EGR and actual EGR.Conditions for Running the DTCThe ignition voltage is more than 9 volts.Conditions for Setting the DTCThe difference between the actual EGR position and the desired EGR position is more than 10 percent for more than 10 seconds.Action Taken When the DTC Sets
Conditions for Clearing the MIL or DTC
Diagnostic AidsExcessive carbon deposits may cause a restriction of movement in the EGR pintle. This problem may be compounded in cold weather with moisture freezing in the valve. Check for full range operation in the EGR system with the scan tool.Check for excessive exhaust back pressure.An intermittent may be caused by any of the following conditions:
Thoroughly check any circuitry that is suspected of causing the intermittent complaint.Test DescriptionNumber(s) below refer to the step number(s) on the Diagnostic Table.