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Discussion Starter · #1 ·
Hi everyone, my 2005 TSX 6mt has thrown a P0420 code randomly a few times. I changed my spark plugs and the code stayed away for 700 miles, until last night. I am looking to find the root of the problem so I started reading up on o2 sensor voltages, LTFT and STFT. Now ive understood that LTFT should be between 0-5. My readings are negative, indicating a lean condition, seems odd as my MPG is pretty bad, I get 22-23 and that is driving so conservatively that it is annoying.

Here are some shots of the obd2 scanner.

Input would be great :)



Thanks!
 

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Before you start with this headache, check the fuses by your feet on the driver's side.

I can't recall what number was blown in mine, #15, I think, on mine. Check #4 also.
 

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Discussion Starter · #4 ·
I bought a new primary o2 sensor.

The car is throwing P0420 which is cat below efficiency. My goal is to find the root problem, generally cat's don't just go bad. That isn't how they are designed.

LTFT: Being a negative value, means the car thinks its running lean therefor it will add fuel as an attempt to compensate for the lean condition. There are no vacuum leaks, so I think my primary o2 at 145k is a little slow these days.

^ Just my theory ^
 
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