Subaru Outback Forums banner
  • Our 4th of July contest is live! Enter HERE for your chance to win a $400 Walmart gift card.
  • Hey everyone! Enter your ride HERE to be a part of this month's Outback of the Month Challenge!

1 - 3 of 3 Posts

·
Registered
2003 Outback H6 w/o VDC Wagon
Joined
·
41 Posts
Discussion Starter · #1 ·
Good evening,

Ever since the engine swap, due to a failed HG, I've been getting intermittent P0420 codes every other week or so. I have a feeling that the passenger side O2 sensor may have been effected, and possibly the CAT.

I ran a few tests with the scanner, and I know I'm probably missing other useful info, but if suggestions are made, I can always make new data sets.

I'm wanting to rule out Murphy gas, since I get 91 always, and try rotating brands when possible. The rear sensor seems rather steady, so the rear CAT seems unaffected.
 

Attachments

·
Registered
2003 Outback H6 w/o VDC Wagon
Joined
·
41 Posts
Discussion Starter · #2 ·
I'm just gonna replace it -- found a deal for the denso upstream for $75 -- couldn't pass that up.

It shipped today, so hopefully arrives by the weekend -- more to come.
 

·
Registered
2001 VDC Wagon - White pearl - 302,000 km
Joined
·
466 Posts
The rear sensor seems rather steady, so the rear CAT seems unaffected.
The rear oxygen sensor(s) is/are not as active as the front ones. You can see a much more active crossover count pattern with the front sensors because it is seeing fluctuations as each cylinder firing comes into the header. The rear sensor gets the "average" mixture of what the front sensor sees, so you will naturally see much slower crossover count activity at the rear sensor. If your HG leak was coolant into the exhaust pipe, it would have to have been leaking for either a very long time, or leaking a substantial amount to permanently "foul" the rear cat.

When you say steady though, you should still be seeing voltages that range anywhere between 0 and 1 volts. .5 volts is the "crossover" voltage. Anything higher than 1 volt usually means a bad sensor.
 
1 - 3 of 3 Posts
Top