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2005 Dodge Grand Caravan displaying a p0409 code during smog check

i just recently had a failed smog check. Pep boys told me i would have to pay $140 to diagnose the problem and then pay for the repairs. They also stated i had to have the repairs completed there otherewise i would have to pay for the smog again. I was under the impression if you failed smog the shop had to retest your vehicle once repairs were complete. I have also researched the p0409 code and am wondering if i can bypass the diagnostic fee and just have a shop repair the EGR valve. If the p0409 code is displaying am i pretty safe in assuming the EGR just needs to be replaced. im trying to save as much money as possible. (FYI: my engine check light also was on at the time. if i would have known i would have got it tested for free somewhere and repaired and then went to get my smog check!)
Answer:

You can do that (have Pep Boys simply change the EGR valve without diagnosis) but be aware they will not take responsibility if your Dodge still fails the test afterwards. The P0409 OBD II Trouble Code does indicate a fault with the EGR circuit, but it doesn't necessarily mean the EGR valve itself is defective. P0409 can be triggered by carbon buildup within the EGR valve passages, faulting or loose circuit wiring, and possible a defective circuit sensor as opposed to a defective EGR valve. We recommend starting with cleaning the EGR valve and the passages first (both through the EGR valve and the intake and exhaust manifolds). There is a simple test you can perform after cleaning the EGR valve and passages using a hand vacuum pump you can buy from an auto part store. Start your vehicle and let it run at idle. Disconnect the EGR valve's vacuum line and apply direct vacuum, in order to open the valve. When the valve opens, if the passages are clean and open, you should notice a large RPM decrease. If the passages are plugged up, you will not see any RPM difference. If there is a RPM decease, then the passages are free, and the next step is to inspect the vacuum signal which is supposed to open the EGR valve. It may be possible your vehicle is not opening the EGR valve at the right time, or at all. If there is no RPM decrease, the passages are still plugged up, or the EGR valve is stuck. You will need to remove the EGR valve and ensure all passages are clean and also ensure (visually) that the EGR valve opens when applied vaccum. posted by SmogTips Support

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