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Catalytic Converter or O2 Sensor, 07 2.5i impreza

Catalytic Converter O2 sensor

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5 replies to this topic

#1 blass001


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Posted 13 November 2013 - 11:47 PM

Hi Everyone!!


I'm in need of some help. I live in California and I bought a 07 Impreza 2.5i (non turbo) about 2 years ago. After my first smog check the car's check engine and cruise control light came on. The cars performance has not changed or the gas mileage so I didn't pay attention to it. Now is time for another smog check and the car wont pass with the check engine light on (I tried reseting but the computer but OBDII picked up on it. too old of a trick). Well now I need to fix the problem but the emissions passed so I'm not sure whats going on. The computer is saying I need a new catalytic converter.

Does anyone have any expirience with this problem? if so SHould I replace or clean the O2 sensors first and see what happens? should I use OEM or after market is fine for 02 sensors or catalytic converter?

I want to be inform since I dont have any expirience with this problem.


Thank you for your time



#2 idosubaru


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Posted 14 November 2013 - 06:13 AM

you do not need a new converter.  unless the converter was damaged they last the life of the vehicle. any mechanic or shop that tries to replace it you should decline and look into options..unless you're okay with that expense.


first step with *any* check engine light is to read the codes and tell us what they are.

how many miles on the car.


if it's an oxygen sensor code - replace the sensor.


if it's a P0420 code then that's a debacle of a code, the worst code you can get, i dread seeing it.  gobs of information on that.

1.  make sure there are no leaks in the exhaust

2.  make sure the engine is running properly and tune up items are in good order

3.  clean out the intake with seafoam

#3 Fairtax4me



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Posted 14 November 2013 - 10:50 AM

There are way too many causes for a p0420 code to just condemn the cats without doing a full diagnostic on the car.

If it passed the tail pipe sniffer emmissions test, the cats are fine.

We do need the actual codes though, since different codes are set because of different issues.
For instance, if you have a code for "system lean bank 1", that could be caused by an exhaust leak or a small vacuum leak. This would also likely trigger a p0420 on a newer car like yours. Replacing an O2 sensor would probably not fix this code, since its caused by a mechanical issue.

#4 blass001


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Posted 15 November 2013 - 04:48 PM

Thank you so much for the advice.


The code was P0442 thank God. Evap Small Leak.The gas cap looks fine so I'm going to try to inspect the EVAP system.

Any advice in how to deal with this besides what i stated above?

#5 Fairtax4me



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Posted 15 November 2013 - 06:10 PM

Evap system has nothing to do with the O2 sensors so leave those alone.

Most of the time this is a bad gas cap, or a pinhole leak on the filler neck due to rust. But with a car so new I wouldn't think rust is an issue. Still worth it to have a look behind the plastic cover on the filler neck in the wheel well.

Check the hoses that lead to the charcoal canister, for cracks or splits, or mouse or squirrel teeth marks.
Try to find the evap hoses under the hood that to to the purge solenoid and the intake manifold (should be on the emissions/vacuum hose routing label on the bottom of the hood) and check them for cracks and splits as well.

#6 StarSubi



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Posted 30 December 2013 - 04:23 PM

Hello! I have a related issue. I bought a '08 Impreza 2.5i four days ago from a dealer. It seemed in good condition, but when I drove it home the cruise control stopped working. Later that evening the check engine light went on. Since I live 2 hours from the dealership, I went into Autozone to have the code read - P0420 catalytic converter :( I took it to a family member's trusted mechanic before taking it back to the dealership, and they're very upset that this dealership sold me this car as the problems are obvious to a mechanic. They discovered the coolant is also leaking somewhere since the tank was almost empty and they couldn't find the leak with a pressure test (and could be affecting the cats). This morning the power steering pump started whining as well - the mechanic saw it had white writing on it and suspects it's a slavaged part. I just dropped it off to the dealership and they're claiming the engine light isn't on. I know they're aware of what they sold me (the salesman couldn't even look me in the eye) and I know they're giving me the run around. I have since found many bad reviews and similar stories on this dealership. Shame on me for not doing more background research. Any advice moving forward?

Many thanks!

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