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08 Outback LL Bean H6 - 236,000 miles
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14 Posts
Discussion Starter #1
I have had the P0420 code intermittently popping up over the past year or two. Earlier this year I noticed my gas mileage starting to get worse, and I am not sitting at 12/20 while it used to be at 18/27. I have replaced both upstream O2 sensors, and a read one that was showing weird voltages. This past weekend, I also started to get misfires, with the car first registering them in cylinder 1, and now in 1, 2, and 6. Along with the codes for the misfires, I am getting a P0026 code. The car doesn't have new oil, but it is still fine and at the correct level. My car's internal code reader also listed both a C0045 and a C0071 codes. I have been trying to chase the P0420 code down with no luck, and with these other codes showing up I am at a loss as to what could be causing this. I am not sure if it is one issue, or multiple issues. But I am not smart enough with cars to piece it together on my own. Also, I bought an ODB2 adapter cable for my laptop, and am using the software that came from it. What could I look at that might give me insight as to the cause of these problems? Also, I tried downloading RomRaider, but it was a lot of stuff and I am worried that I might mess something up using it. However, if it really is the best for this stuff, I'll try and figure it out. Thank you for any input any of you might add.
 

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Premium Member
2001 VDC/SC One of a Kind
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12,456 Posts
There's a link in my signature for P0420. Have you been through that thread?

C codes generally mean poor electrical flow. How old and what condition is the battery in? How much corrosion is in the battery cables and clamps? Poor electrical flow can also create the misfires, P0420 and other issues.

Rom Raider is the best thing for logging data. You can even save the logs and post them up on Google Drive and link it on the P0420 thread. Then I can see what the car is doing.

We would prefer to keep the P0420 Diagnosis thread going for all things related to this code. I know it's long but it keeps things stacked together.
 

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Registered
08 Outback LL Bean H6 - 236,000 miles
Joined
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14 Posts
Discussion Starter #3
I'll migrate over to that with a link to this post! Thank you! And I have, it's just a lot of info and I am new to using a computer with my car. I will try and figure out RomRaider and hopefully get something going with that! Also, my battery is 2 1/2 years old, and I recently cleaned and greased the positive connector.
 

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Premium Member
2001 VDC/SC One of a Kind
Joined
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12,456 Posts
Grease or any silicate is bad. You want a clean connection between the post and clamp. If you battery develops a "fuzz" then it needs to be replaced. That fuzz is acid leaking out if the battery and nothing will prevent or stop it. If you want to have something to resist corrosion then spray paint the clamps after you attach them to the post.

Don't know about where you are, but down here batteries start on the downhill run at about 2.5 yrs on average.
 
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