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Having a few new problems with my 2003 Mercury Mountaineer.It has the 4.6 L engine.In the last couple of days I have got two new codes.PO 401 Exhaust Gas Recirculation (EGR) Valve, insufficient flow detected.Also PO 402 Exhaust Gas Recirculation (EGR) Valve ,excessive flow detected.Wondering how I can check the EGR to make sure this is the problem.I did put a new exhaust system on the truck before this happened but I don't see how that could be the problem.Is there something else that could cause this maybe I should be looking at. Thanks

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  • fxrsmike Aug 03, 2010

    Excellent.I did not even think of checking for that type of sensor.
    Thanks for the help !



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This is usually not the EGR vavlve itself but the sensor which detects the flow. If it is reading low and high at the same time, it is probably going to be the sensor used. The DPFE is usually located on the side of the engines intake manifold(driver's side). Will be about 4" wide(as you are looking at it)by about 2 1/2" high, will have 2 hoses going to it coming from the exhaust manifold. If both of these hoses are hooked up and in good condition, replace the DPFE( this stands for differnetial pressure feedback, exhaust). This is a common failure and most parts houses carry this sensor in stock. Auto zone carries these for around $40. If it is just the hoses, you may have to get the hoses from your local Ford dealer. These are special hoses made to take the extreme heat of the exhaust system.

Posted on Aug 02, 2010


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The pipes are supposed to have pressure in them when the EGR valve is open, but sometimes, with the EGR closed may have vacuum... the DPFE compares the pressure/vacuum values from the 2 pipes (these 2 pipes take their pressure before and after an orifice) and knows how much recirculated exhaust gases go through the engine...

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