O2 sensors in OBDII reader.

[drsmisss]

Hey all, ive got the famous p0420 error code in my 2008 legacy, 2.5i, EJ253 engine. I'm not so sure its the cat that's the culprit.
Looking at the obd reader, i'm only getting readings from one of the 02 sensors Bank1 sensor 2. Does anyone know if this is normal? If not, im guesing, hoping, that its a faulty sensor throwing the error.

 

[bmart]

Almost never cat. Almost always the sensor.

 

[drsmisss]

Almost never cat. Almost always the sensor.

yeah i figure that too, is there a way to know from the OBD readings if the first sensor i bad? the readings from the second is good when idle so i dont think it's the cat.

 

[bmart]

I have also had the code arrive and then go off for years without doing anything like in one of my cars now (5k miles and still out!). In general, I think they're ~$100 plus the special install tool which you can likely loan from the local store if you don't have access to one.

 

[drsmisss]

I have also had the code arrive and then go off for years without doing anything like in one of my cars now (5k miles and still out!). In general, I think they're ~$100 plus the special install tool which you can likely loan from the local store if you don't have access to one.

ah thanks, yeah the cars run for 230 000 km's now so i'm not spending the 600 usd on a new cat anyway. I'll continue deleting the error codes and pretend like nothings wrong

 

[GuyS1]

What is your Subaru like with fuel consumption? Any noticeable changes? Could it be the O2 sensor has not been doing it’s job and the car running too rich? Overly rich is problematic for cats, but certainly not the only precursor to a plugged up cat.