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My 2009 NA outback, almost 100k on it was throwing cat inefficiency P0420 codes. I tried running paint thinner through the tank a few times, it made the problem go away for a for weeks, but it has returned reliably. I then tried the low pass filter trick on the secondary o2 sensor, it is now throwing P2096 CEL code - Post Catalyst Fuel Trim System Too Lean.

I definitely cannot afford to replace the cats on this thing at this point in time.

I ordered a tactrix cable to disable the mil codes via ecu reflash, and while Im at it, maybe slight tune for my afr intake. Problem is, I have no idea if this is even a viable route.
I've got a primitive racing suspension on it, cobb short shifter, and its an MT, what can I say I'm attached.

Any words of wisdom for this cornered NA outback owner?
 

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2005 Outback R LL Bean 3.0 H6 w/ 5 speed sport shift
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You really need to have a means to watch the live data from your sensors and fuel trims. Stay away from the Youtube hacks like the paint thinner, multiple tests have shown they really don't work.

I seriously doubt you have bad cats. I've researched this intensely and my own experiences have been that unless the cats are loaded up for an extended period, they usually aren't the problem, more often dirty sensors, bad sensors or bad connectors. If you haven't pulled and cleaned the sensors since your paint thinner treatment, I'd do that first. I've used electrical component cleaner (you can get it at the parts store or wally world), spray the sensor down thoroughly letting the cleaner drip out and then use some compressed air to completely dry it before you reinstall and put current to it.

Until you get the permanent and temp codes erased, you're going to have a hard time diagnosing the core problems. These codes are stored and pop up confusing the process.

Last thing you want to do is replace the cats. One thing you can do to determine if the cats have degraded is to use the heel of your hand and bump the exhaust where the cat is housed to see if it rattles. However, if it's loose, you've probably already heard the rattle.

As everyone on here will attest, the P0420 code will drive you nuts if you let it! It's a detective type of process, but the good news is, it's not usually critical to your engine's long term health.

These are my opinions, many other's on here have a much more advanced understanding of these processes. I learn stuff every time I'm on here!
 
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