Cam Posted January 27, 2019 Share Posted January 27, 2019 Trying to buy a Subaru Impreza 5 door hatch, 2006. Tidy car, everything seems to be running fine. Had the timing belt, clutch and headgasket replaced in November 2018. no check engine light showing up but plugged in a code reader anyway and it says P0420- catalyst system efficiency below threshold (bank 1) asking for advice need to know in an hour Link to comment Share on other sites More sharing options...
GeneralDisorder Posted January 27, 2019 Share Posted January 27, 2019 Needs a cat. Probably also a PCV valve. Going to cost about $1200 GD 1 Link to comment Share on other sites More sharing options...
ocei77 Posted January 27, 2019 Share Posted January 27, 2019 The p420 is generally a benign code that usually requires replacement of the front o2 sensor and or is the result of an exhaust leak. Rarely but sometimes is needing a cat replacement. O. 1 Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted January 27, 2019 Share Posted January 27, 2019 on an '06, the rear sensor may be more than just a cat conv 'nanny'. best to be prepared for a new cat but, catching up on any lapsed maintenance and examining for exhaust leaks, vacuum leaks and anything else that may throw-off the a:f ratio is important. 1 Link to comment Share on other sites More sharing options...
ocei77 Posted January 28, 2019 Share Posted January 28, 2019 Bank 1 is the front sensor O. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted January 28, 2019 Share Posted January 28, 2019 Bank 1, sensor 1 is the front. Bank 1, sensor 2 is the rear. That Subaru has only one bank. O2 sensors may need to be replaced as well, but in all likelyhood even after that it will need a cat. Damage has been done. GD Link to comment Share on other sites More sharing options...
bodhicheetah Posted January 31, 2019 Share Posted January 31, 2019 (edited) Deleted my post...posted new topic... Edited February 2, 2019 by bodhicheetah Link to comment Share on other sites More sharing options...
Recommended Posts
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now