RheaCo.Legacy Posted August 16, 2017 Share Posted August 16, 2017 I bought a 2009 Legacy 2.5. The check engine light came on the day after I bought it. It is a bad catalytic converter. It's a thousand dollar fix, & I've heard the bad cat code could come back. I've been driving it & clearing the codes once a day. I'd appreciate any suggestions? Link to comment Share on other sites More sharing options...
MilesA Posted August 16, 2017 Share Posted August 16, 2017 If you are getting P0420, that is not necessarily a bad cat. It can be caused by a number of different things. Just swapping parts in could be expensive and unnecessary. The best thing to do is troubleshoot the problem before you replace any parts. Either you or a competent technician needs to go through a diagnostic procedure; you can download info for your car here: http://legacygt.com/forums/showthrea...ix-171435.html The cause could be such things as: -bad front oxygen sensor -bad rear oxygen sensor -faulty wiring -exhaust leak -bad catalytic converter Just resetting the ECU is not going to do any good. It can make the car run worse until it relearns and it hides any stored secondary DTCs you may have. Link to comment Share on other sites More sharing options...
apexi Posted August 16, 2017 Share Posted August 16, 2017 What state are you in? http://www.wqd40.service-campaign.com I think certain states also have a 15yr/150k pzev emissions warranty. Link to comment Share on other sites More sharing options...
RheaCo.Legacy Posted August 20, 2017 Author Share Posted August 20, 2017 TN. It has over 250,000 miles. The guy I bought it from said he put an o2 sensor on it. Link to comment Share on other sites More sharing options...
MilesA Posted August 20, 2017 Share Posted August 20, 2017 TN. It has over 250,000 miles. The guy I bought it from said he put an o2 sensor on it.You should still go through the logical process of troubleshooting the issue. Try to figure out what is wrong before swapping parts. Assuming things can get expensive. Link to comment Share on other sites More sharing options...
RheaCo.Legacy Posted August 21, 2017 Author Share Posted August 21, 2017 So do I take it to Subaru, & let them run the diagnosis on it? Link to comment Share on other sites More sharing options...
RheaCo.Legacy Posted August 21, 2017 Author Share Posted August 21, 2017 Thanks for all the advice Link to comment Share on other sites More sharing options...
apexi Posted August 21, 2017 Share Posted August 21, 2017 After that many miles, I wouldn't be surprised if it was the cat. The dealer will probably just say the cat is bad, and I'd imagine you'd get charged around like $100 for their diagnosis. What confuses me is whether you need a cat that's legal for use in CA and NY, or if you can just get any old cat. I think if the label under the hood said pzev, you need a CA/NY cat? I'm not sure about that though, I wonder what the label under your hood says. Link to comment Share on other sites More sharing options...
MilesA Posted August 21, 2017 Share Posted August 21, 2017 So do I take it to Subaru, & let them run the diagnosis on it?Many competent auto technicians can do the diagnosis as long as they refer to the information in the service manual. http://legacygt.com/forums/showthread.php/vacation-pix-171435.html You can find the info by searching the manual for references to P0420. The way the car detects and throws this code should be found in section: GD(H4SO). The diagnostic procedure should be found in section: EN(H4SO U5)(diag). They can troubleshoot this without the Subaru Select Monitor tool described. The gist of it is checking the front and rear oxygen sensors and wiring, monitoring output voltage of each sensor while the car is running, and looking for exhaust leaks. The catalytic converter might be faulty if problems are not found elsewhere. Hope that is useful. Link to comment Share on other sites More sharing options...
RheaCo.Legacy Posted August 23, 2017 Author Share Posted August 23, 2017 Thanks for all the info. I'll check under the hood. I work next to Maxi Muffler & Auto, & they looked at it, & told me it was the cat. It was going to cost more there than at Subaru. Link to comment Share on other sites More sharing options...
MilesA Posted August 23, 2017 Share Posted August 23, 2017 I work next to Maxi Muffler & Auto, & they looked at it, & told me it was the cat. It was going to cost more there than at Subaru.A lot of shops just assume that it is the cat, but 8 out of 10 times they are wrong. It is usually an oxygen sensor, which is a heck of a lot cheaper and easier to replace. Link to comment Share on other sites More sharing options...
RheaCo.Legacy Posted August 24, 2017 Author Share Posted August 24, 2017 Preciate it brother. I'll let ya know how it goes. Link to comment Share on other sites More sharing options...
08SpecB_DE Posted August 24, 2017 Share Posted August 24, 2017 The catalyst on the hood will tell you if the car is compliant to California emissions or if it's just federal. Link to comment Share on other sites More sharing options...
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