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

 

 

Needs a cat. Probably also a PCV valve. Going to cost about $1200

GD

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.

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.

Bank 1 is the front sensor

 

O.

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

Deleted my post...posted new topic...

Edited February 2, 20197 yr by bodhicheetah