[DaveL]

same results again

I tried again, this time with the fuel system status indicator, and even when it was indicating CL (I assume for closed), I was getting essentially the same results as described in my first post.

Could these results be related to my need for a head gasket replacement?

 

[DaveL]

not sure how to add ground

Thanks for the suggestion, but I am using an OBDII cartridge (ELM327) sending info via WiFi to the Dash Command software, so don't think there is a reasonable way to ground that system directly to the battery.

Maybe I should just hook up a meter to the front O2 sensor directly to see what readings I get that way. Might be able to try that sometime during the week.

Odd thing is that there are two other posts in the past week or so reporting similar readings.

 

[DaveL]

Are your head gaskets leaking?

Yes - an external oil leak. No internal coolant leak as far as I can tell.

I am trying to decide whether to just get the head gaskets done or go with a rebuilt engine (leaning towards rebuilt, but not yet quite convinced that it is worth the extra cost). I got this car a few months ago and am sorting out several issues at the same time - though I am starting to lean toward waiting until I get the head gaskets done before sorting out the cat/O2 issues. I have an inspection sticker good for another 9 months, so no rush.

 

[DaveL]

I do not know if Subaru's kick a O2 specific code or it throws O2s, cat other emissions problems into the P0420 code?



just get a quality replacement if you have to swap it out.

There are separate O2 sensor codes, but I don't know if the car also throws other issues in the P0420 code. The car stopped throwing the rear O2 sensor codes when I replaced the rear O2 sensor. I also replaced the front.

I have been trying to research the "quality replacement" issue and so far have come up with Bosal and Eastern Catalytic as reasonable choices. Any suggestions?

 

[DaveL]

If some of the oil & coolant is getting burned, that could damage the O2 sensor(s).

Has your gas mileage dropped off or is there a drop in engine performance?

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]

Engine performance seems fine. It was in this condition when I bought it, so don't know if the mileage is off. I am still on my first full tank. As far as I can tell, the head gasket leak is only an external oil leak. If there is any other oil loss or coolant loss, it is extremely slow - so hopefully I am not damaging my new O2 sensors. They have completed their check cycles and not thrown any codes.

 

[DaveL]

One thing about it if you fix the cat a lot of times other fuel/ air problems could be behind it.

Eastern cat is a good one to go with but you have to keep in mind that once you replace the cat on this car, you need to be willing to fix the other fuel or air issues CELs as well since those issues will and do burn up your new cat. I had this happen on my 99 Miata the cat emissions code masked an EGR code and a crank angle position sensor code. These other issues will need to be addressed before you put 50-100 miles on the new cat as it could kill the new cat as well.

good luck ...

This kind of issue is one reason why I am thinking in terms of getting the head gaskets fixed before I keep chasing the P0420 code. The car did throw a crank position sensor code recently. I cleared it and it has not returned, but there may still be an issue there - hopefully just a dirty sensor.

 

[DaveL]

Okay... I was trying to find the reason for the CAT(s) failing. Burned oil + coolant could do that. Running an Air/Fuel mixture that's too rich will also kill a CAT! :icon_eek:

I did a quick reread of this thread & I may have missed it, but are the O2 sensors Denso?

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]

Both O2 sensors are OEM (from a dealer) with less than 200 miles on them. I think the prior front O2 was also OEM. The rear, however, which was throwing a code, was a Bosch. The prior owner said he had that Bosch installed about a year ago.

The front O2 reading, if correct, suggests to me that the car is running too rich, but I have not yet investigated how to fix that. I don't know how it was reading with the prior front O2 sensor as I did not have the equipment to read the voltage before I changed it out.