SubeeTed Posted September 29, 2021 Share Posted September 29, 2021 SO I have a 2005 Legacy Wgn with about 2005,000 miles on it . And of course the CEL is on ! Well it's always code P0420 , “Catalyst System Efficiency Below Threshold (Bank 1) , Ya, YA ! So I'm in Massachusetts and the car is 16/17 years old . CEL doesn't matter anymore for inspection ! I have been doing a lot of highway driving and like to use my cruise control , so what I do is get my handy-dandy OBDII checker and clear the code and then you can use cruise again 50 about 50 miles, which works for me ! Well that's getting old ! So I'm thinking of actually fixing bank 1 ! I know there are dozens of systems out there, Ebay junk, the big box parts stores etc. My mechanic says that Subaru OEM bank 1 is the only one that lasts , it better for $1,200 ! Well my question IS, is there any decent after market bank 1 out there ? And just WHO makes Subaru OEM bank 1's , maybe get it direct? The car runs fine, getting great gas mileage ! Quote Link to comment Share on other sites More sharing options...
brus brother Posted September 29, 2021 Share Posted September 29, 2021 (edited) wedge a brick against the gas pedal for cruise control and keep driving? at "2005,000" miles you are well past end of life? Edited September 29, 2021 by brus brother Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted September 30, 2021 Share Posted September 30, 2021 bank 1 ? Not sure ifa 2005 is using post cat data for a:f adjustment or not. If it doesn't, you might be able to use a 'spark plug extender' - to fool the rear sensor. Quote Link to comment Share on other sites More sharing options...
brus brother Posted September 30, 2021 Share Posted September 30, 2021 5 hours ago, 1 Lucky Texan said: bank 1 ? Not sure ifa 2005 is using post cat data for a:f adjustment or not. If it doesn't, you might be able to use a 'spark plug extender' - to fool the rear sensor. Didn't work for me on my 2005 OB. I still have the drilled out spacer if someone needs it. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted September 30, 2021 Share Posted September 30, 2021 if we 'assume' (dangerous I know, but a starting place....) EITHER; 1. the cat is not 'lighting off', or, the sensor is unable to report correctly (bad, cut wiring, etc.); I have never needed to to try it, but if the cat is NOT working, the temp at its output will be the same or lower than the inlet side. If it IS working, the temp at the outlet will be HIGHER (by maybe 100*F) than the inlet. Try some measurements at the pipes with an infrared therm. Or, get live data and look at the sensor's voltage. One sometimes overlooked cause of P0420 is exhaust leaks. 1 Quote Link to comment Share on other sites More sharing options...
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