Got PO420 need some advice

[dodik]

so yesterday i've got PO420 Catalitic System Efficiency Below treshold (bank 1), i promtly dleted it to see if it comes back about 50 milese later still not lighting up. i remember that for my fathers taurus to run a full cat system scan i had to drive it at a constant speed 40-50 mph for about 15-20 minutes, does subaru have the same thing or not. Also my tranny started acting a i little funny last week, when it shifts from 3-4 rpms jump, if i drive gently and it starts to shifts at 2k rpms it will rev up until 3k and only then shift. could those two be related? this carp is bugging me out lol.

[Huffer]

You have fish bugging you out? :lol:

The Subaru ECUs take about 50miles of "regular" (whatever that means) to run a full duty cycle of tests on all the sensors. It does this all the time. If a sensor fails three times in a row (depending on the test being run by the ECU), it'll trip a CEL.

Normally a P0420 is due to a failing O2 sensor - sometimes it's the catalytic convertor depending on the age and condition of the cat.
An exhaust leak pre-sensor can cause this CEL also.

The tranny shifting could be a sign that it's not engaging under load.

[dodik]

[quote="Huffer"]You have fish bugging you out? :lol: quote]

yeah i a little i haven't caught one in a while lol

thanks for the info, i replaced both front afr sensors one last summer one this summer haven't touched the rear one yet the codes where different, i guess ill drive and wait if it comes back or not.
Tranny actually does engage under load meaning if i drive more spiritedly it shifts just fine with no hesitation its if there isnt much load it does it.

[ScoobySnack]

Any aftermarket headers? Once I put on my borla I got the code after 40 miles since the flow is much greater. I bought new o2 both of them and it still did not turn off the code so I had to do the spark plug foul mod to the second o2 to make it go away. Hope that helps. Or you can get a scan guage 2 and clear it e everytime it shows up. Good luck

[dodik]

no unfortunately there are 0 aftermarket headers for my car except for stock stainless replacement.