[Eric]

Eric,

Thanks for posting this video. I’m having a problem on my 2005 Subaru Legacy. I’m getting the P0420 code which caused a CEL to come on and disabled my cruise control. :pinch: After watching your video, I made a trip to autozone to barrow there code reader so that I could measure the O2 sensor voltage. I also used an IR thermometer on the input and output of the cat. The temperature test showed about 400deg on the input and about 500deg on the output (suggests cat is working). But I noticed something very odd on the O2 voltage readings. The down stream sensor moved in range a between 0.2 to 0.8 volts. I assume this is why the code got set. But the upstream voltage read a constant 2.75V. Does this mean the upstream O2 sensor is bad?

The only other code that got set was on saying something about a loose gas cap.

Any help appreciated.
Thanks!

[Author]

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