I have a 06 Armada with 103000 miles. About 3 weeks ago my check engine light came on and I took it to Auto Zone and they told me the code was P0430. Right around the time my check engine light came on my engine felt like it would misfire. My buddy cleared the code for me and it hasn't come back since. My engine also seems to be accelerating fine. Problem now is that I am getting horrible gas mileage, around 10MPG. Most of my driving is highway. I tried to set up an appointment with the dealership and the service advisor told me there was nothing they could do to trouble shoot unless the check engine light is on. Does anyone have any suggestions on what the issue might be or somewhere I can take it to find out what the problem is? I realize that it could be a bad cat, O2 sensor or a cracked manifold but I don't know where to start.
If you are getting efficiency codes there really is only 2 options...exhaust leak upstream of the converter(s), which can introduce oxygen to the exhaust or you have converters that are not working well enough to keep rear oxygen sensor from switching. Probably the best place to start is to have someone pry the covers back on the manifolds and look for cracks you will probably find them......although technically there does not have to be cracks for the 420/430 codes. You mentioned oxygen sensors while you may or may not have a problem with an o2 sensor it can not set a efficiency code.
I tried the ECU air/fuel re-learning procedure and still haven't had any improvement in gas mileage. I have an appointment with the dealership tomorrow to check for any exhaust issues. Hopefully the fix won't be too expensive. I'll post their findings tomorrow.
They recommend changing out both CATS for 2835 and my MAF for 495. I'm going to do the MAF myself for now and decide whether to trade it in or put the money in for the fixes. Thanks for all the input guys.
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