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bill, dodge master tech
Category: Dodge
Satisfied Customers: 1632
Experience:  25 years with dodge drivability and electrical expert
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Can you help with code P0406 on 08 Ram Big Horn, 5.7 Hemi?

Customer Question

Can you help with code P0406 on 08 Ram Big Horn, 5.7 Hemi? If yes, I'll give you the info I have so far.
Submitted: 2 years ago.
Category: Dodge
Expert:  bill replied 2 years ago.
hi i'm bill
welcome to just answer
please remember I am NOT there in front of you! my answers are based on your information.
p0406 is a failed egr valve 99% of the time, the sensor is a PART of the egr valve, if you replaced it before with an aftermarket one I would use an oem one, and be sure the battery is disconnected when you replace the valve, this will clear the egr counts in the engine computer and prevent it from setting false egr codes, also have the engine computer software verified it is at the latest level, this can be done either at a dodge dealer or at a shop that has the equipment to perform reprogramming, the cost should be around 1 hours labor
Customer: replied 2 years ago.
Thank you so much for your quick response! The EGR is from an auto parts store, and I believe a direct replacement. I.E. Not super tuned or for better performance than OEM. I do realize the sensor itself could've gone bad even if the EGR valve is ok, and I'll replace it if need be, just wanted to make sure that was the issue. Do the voltages read out on the perspective pins given the conditions I listed?
Expert:  bill replied 2 years ago.

you don't say if the code is stored or active, and when you tested was the code stored or active the readings you have are meaningless UNLESS the code was active at the time you tested the system.

we use egr more for performance than emissions because with an egr valve we can use a HIGHER COMPRESSION AND FAR MORE AGRESSIVE timing curve than without it

remember with the obd2 rules in place anytime a fault is detected the check engine light has to be illuminated and then the system is tested by the computer if it continually fails the test the code is considered active if it passes th etests 3 times the light is turned off, if the computer passes a test 1 time the code is considered stored but the light stays on until 2 more tests are passed .

so it is critical any tests are done with an active code

BUT egr valves are common to fail and I would be very confident in replacing the valve with a good oem one as there have been many updates to the original design

Customer: replied 2 years ago.
My apologies. The fault code was active the entire time I measured voltage and continuity. The code was intermittent at first, a few months ago, but since then has been active constantly during key on and engine running, and so was the case for my measurements earlier tonight.
Expert:  bill replied 2 years ago.
then those readings do point to a failed egr, again I also must emphasize having the engine computer software verified and updated as needed there have been many enhancements since 2008 when your truck was new also remember have the battery disconnected (very important) when you change the egr or you may set ghost egr codes
Expert:  bill replied 2 years ago.

just following up to see if you still need assistance

Customer: replied 2 years ago.
I'll be replacing the valve within a week. Once that happens, if it clears the fault code then I'll close this thread and pay you out. And yes, anytime I do anything electrical I always disconnect the battery. I work for an engine company as an electronic tech, so I'm quite familiar with electronics and how they work, just wasn't sure if the voltages I was seeing were correct. If this code more often points to a bad EGR or sensor, then I'll go ahead and replace it. It would make me feel better to know it's that and not my actual truck having electrical issues.
Expert:  bill replied 2 years ago.

many people just clear the code including many tech's it wasn't until ghost codes were showing that the addition of disconnecting the battery was added through a engineering bulletin.

I look forward to hearing from you, and please don't forget to verify the engine computer software

Customer: replied 2 years ago.
Sure thing. And I suppose I should've told you that the battery had been disconnected and the code remained.
Expert:  bill replied 2 years ago.

that is ok that also just points further to a failing egr