I've replaced the EGR valve on my 2009 mercury mountaineer but still get the P405 error.

Question

2009 4.0L Mercury Mountineer. Read a P0405 code, so I replaced the EGR valve. Still getting the P0405 code. I can't find enough info online to know which sensors or wiring I need to check for this year/model. Any suggestions?

Answer 1

P0405 EGR (Exhaust gas recirculation ) circuit A low

This code is not for the EGR valve it for the back pressure EGR what it is called is Differential Pressure feed back.pressure sensor ,

Comments

But unless I'm mistaken, the DPFE is integrated wiht the EGR valve.  Seems unlikely the brand new EGR valve would have the exact same defect as the one I replaced.  What else could affect this signal?

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Not on this year make and model , if you have the integrated EGR you would also set a MAP sensor code, P0405 is always the DPFE type system Mercury 4.0 uses the DPFE. there the 4.6 and the 5.4 that uses the integrated EGR system These are the lincolns and the Ford. I have a fleet for a taxi account and non of them uses the integrated EGR, there is a DPFE on it

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Here is a picture: http://www.autozone.com/emission-control-and-exhaust/egr-valve/duralast-egr-valve/184224_0_0
There is one, 6-pin connector that includes both DPVE and EGR valve sensors.  The wiring diagram shows them going to the PCM.

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This is the ESM, the DPFE is also the MAP sensor. Just because you set a P0405 which is circuit low. There two hose that attaches to the ESM or EGR, one of them should have manifold vacuum just check that first before you even decide it is electrical. Just because you set a P0405 that can mean that the ECM is giving the signal and proper power and the EGR doesnot respond P0405 can also mean there is no EGR flow. This does not even have to set a no to low flow EGR gas. unless it is fully plugged. a partial plugged can set a P0405. Try this also on the EGR  system there should be a EGR vacuum solenoid. there a cap there take the cap out, there you would see a nozzle. with the engine running put you finger on the nozzle this would cause vacuum to go to the EGR and will open the EGR and allow recirulation gas into the intake this make the rough idle. if it does not your EGR is plugged.provided there is vacuum to one of the lines that is suppose to be manifold vacuum.