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The rest of my post that vanished while trying to complete it said something like this; Alaska is a VERY popular place to drive Subarus, so in all the years working on the independent side I had the opportunity to work on many of them, after 20 years I ended up working for the dealership here. During my time at the dealership I saw a tremendous amount of them for P0420 DTCs, suffice it to say that Subaru has a high failure rate for the cat. convs and the O2 sensors, often they all would be in fail mode by the time they made it to us as they can and do directly affect and effect each other.
This spans several model years and when I left there, there was no improvement in sight. Hopefully they have it squared away now, or will soon.
I wasn't in your environment working on Subies ... but in over 35 years of working on my client's Subie's as an independent shop in Colorado, I never saw a failed catalytic converter on any one of the cars I saw; every one of them had O2, poor maintenance, or wiring circuit failures.
Of course, I only saw these cars after they'd been through years of warranty/dealer service departments. So they may have had a cat replaced before I ever saw them. Typically, I didn't see a car until it had at least 100,000 miles on it and some years of service.
On my own personal Subie's ... after several 1995 & 1996 OBW's (and a very high mileage Brighton), and now a pair of 2000 and 2001 OBW Limited's ... all of them with at least 250K miles on the clock before being sold or traded off ... I've not needed to replace a cat. Every time I've had a CEL come on and the DTC code for a cat operating below efficiency, it proved to be other issues which corrected the problem and kept the CEL off for years afterwards. I've not bought one car with less than 120,000 miles on it, and frequently find that they have the original rear O2 sensor even though the front sensor has been replaced.
I wasn't in your environment working on Subies ... but in over 35 years of working on my client's Subie's as an independent shop in Colorado, I never saw a failed catalytic converter on any one of the cars I saw; every one of them had O2, poor maintenance, or wiring circuit failures.
Of course, I only saw these cars after they'd been through years of warranty/dealer service departments. So they may have had a cat replaced before I ever saw them. Typically, I didn't see a car until it had at least 100,000 miles on it and some years of service.
On my own personal Subie's ... after several 1995 & 1996 OBW's (and a very high mileage Brighton), and now a pair of 2000 and 2001 OBW Limited's ... all of them with at least 250K miles on the clock before being sold or traded off ... I've not needed to replace a cat. Every time I've had a CEL come on and the DTC code for a cat operating below efficiency, it proved to be other issues which corrected the problem and kept the CEL off for years afterwards. I've not bought one car with less than 120,000 miles on it, and frequently find that they have the original rear O2 sensor even though the front sensor has been replaced.
Thanks for the lengthy summary. You wrote that cats. rarely fail in these cars, however when I replaced the cat., the CEL was off continuously for 6 months.
The Ignition wires and air filter was changed when the cat. was done.
The car runs fine... You wrote to replace the O2 senors...2 questions: Can the sensors be tested by just removing and looking at them? (2) Would the front or rear seem to be the culprit based on the fact that the car runs fine.
Thanks for the lengthy summary. You wrote that cats. rarely fail in these cars, however when I replaced the cat., the CEL was off continuously for 6 months.
The Ignition wires and air filter was changed when the cat. was done.
The car runs fine... You wrote to replace the O2 senors...2 questions: Can the sensors be tested by just removing and looking at them? (2) Would the front or rear seem to be the culprit based on the fact that the car runs fine.
1) No, unless it was visibly damaged upon inspection. The way to test them is too actually monitor them with a scan tool,. laptop, or DVOM.
2) The car may seem to turn fine by your operation and perception, but it can be operating outside the parameters set within the ECM at trigger a DTC wjile being completely undetectable to you otherwise.
Quote:
Originally Posted by sunsprit
I wasn't in your environment working on Subies ... but in over 35 years of working on my client's Subie's as an independent shop in Colorado, I never saw a failed catalytic converter on any one of the cars I saw; every one of them had O2, poor maintenance, or wiring circuit failures.
Of course, I only saw these cars after they'd been through years of warranty/dealer service departments. So they may have had a cat replaced before I ever saw them. Typically, I didn't see a car until it had at least 100,000 miles on it and some years of service.
On my own personal Subie's ... after several 1995 & 1996 OBW's (and a very high mileage Brighton), and now a pair of 2000 and 2001 OBW Limited's ... all of them with at least 250K miles on the clock before being sold or traded off ... I've not needed to replace a cat. Every time I've had a CEL come on and the DTC code for a cat operating below efficiency, it proved to be other issues which corrected the problem and kept the CEL off for years afterwards. I've not bought one car with less than 120,000 miles on it, and frequently find that they have the original rear O2 sensor even though the front sensor has been replaced.
The model years that had the high failure rates were 2000 and later, and being at the dealership the great majority of vehicles that enter the shop are under factory and or emissions warranty, unlike what you/I saw on the independent side after they are beyond factory coverage. Also, 2 subarus of the model years 2000 and 2001 for you does not a sample make compared to the hundreds of Subarus of those model years and later that I saw. I do not mean to imply that all of the cats and O2 sensors will fail, merely that is a high rate of failure.
What's the environment this vehicle is in? I saw Alaska, but don't think that's where the OP was?
Before just throwing parts at it.. I'd have a visual inspection of the exhaust system, pre-cat.
I live in a non-emission, non-inspection state.. So.. My truck started throwing a P0420(As I recall, that was the code, it was the Catalyst System Below Efficiency code.. Sounds right) code right at about 105k miles (juuuust outside of warranty).. I wasn't having any performance issues.. No noises coming from the cat (Previous truck, a 97 S-10 had the catalyst come loose and start rattling around).. So.. I just let it be..
Back in mid December.. After about 5 years and 60k more miles.. I started noticing a vibration/rattle at between 1300-1600rpms or so.. Figured it was a heat shield on the exhaust somewhere coming loose.. Next time I had it on a rack.. Preferably in the summertime.. I'd check it out..
Within a month.. while stuck behind some assclown doing 15mph in a 40mph zone where I had to keep feathering the gas.. I found the answers to all my questions..
I found out that my Colorado has 2 Cats.. One of which is built into the exhaust manifold. I found out that apparently the vibration was a crack getting bigger and bigger on a weld joint where the first cat attached to the exhaust manifold. I already knew that running a vehicle with no muffler is very loud.. I found out just how loud it is with basically no exhaust manifold attached..
That crack finally broke the entire weld.. Got a new exhaust manifold.. And apparently that old one had been the P0420 problem the entire time.. Because no SES light after replacing the exhaust manifold.
So.. It's possible, especially if you live in a 'high salt' area or something.. That you've developed a leak prior to the cat in your exhaust system.. And that's what the system is detecting.
Most car owners (and some mechanics) haven't learned the lesson yet that computer codes point you to an area where the problem is.. Not at the problem. Something I don't overly fault mechanics for, but many are guilty of.. They see a code and replace the part with no diagnostics. Lots of times.. It's fine.. I mean, you deal with 20 cars that all throw the same code and the same solution fixes them.. You're probably going to do it on the 21st that comes through the doors. But sooner or later.. You'll get bit by it.. Not that I have a better solution.. What are you going to do? 2 hours of diagnostics to confirm the problem? Not worth it on a $50 part that takes 15 minutes to replace.. But.. You swing and miss on a $1500 job.. People get upset for some reason.
OBDII is better than OBD I by a long shot, it mandated that all manufacturers display and allow access to repair facilities a standard set of data as well as a standard for the Data Link Connector and it's location. It also eliminated alot of cryptic terminology and proprietary terminology and leveled the playing field for the independent repair facilities in the USA.
For those who get grease under their finger nails a simplified signal platform standard such as obd2 is superior. For those of us who tune for those with grease under their finger nails obd1 is easier. Having to send a pcm back & forth to reflash vs burning a plug in chip made it much more difficult for the aftermarket vs sending a chip. Please feel free to live in you're own perceptions, but for me I'll take obd1 any day. There's not one single GM code different between the for like designs. As designs progressed so did codes. In other words, look at 95 to 96 Corvette and you'll see no difference except Datsun was brought up to an American standard.
For those who get grease under their finger nails a simplified signal platform standard such as obd2 is superior. For those of us who tune for those with grease under their finger nails obd1 is easier. Having to send a pcm back & forth to reflash vs burning a plug in chip made it much more difficult for the aftermarket vs sending a chip. Please feel free to live in you're own perceptions, but for me I'll take obd1 any day. There's not one single GM code different between the for like designs. As designs progressed so did codes. In other words, look at 95 to 96 Corvette and you'll see no difference except Datsun was brought up to an American standard.
You do realize that the Europeans build a car or two, yes? That aside, the after-market world is just that, after-market.
Also, OBDII is not "my own perceptions", it is a Federal Mandate, it is fact, and as you have stated affects you negatively (per your perception). Why would GM, or any other manufacturer, have different codes between their models anyhow?
And.... as far as the after-market world goes, they are beholden to no entity, but to play it smart most after-market manufacturers produce parts that are CARB compliant so that they are more marketable and come in line with emission standards for purely economic reasons, a much larger market than purely off-road or race track.
As for Datsun, there was no Datsun when OBDII became effective, Datsun ceased to exist in 1986, then in 2013 was reintroduced in markets other than the U.S.
Could it be an O2 sensor? there are 2. The generic p0420 code seems like it needs to be more specific.
The most likely culprit is one of your O2 Sensors - probably upstream. It's remotely possible that you could have a vacuum leak, a partially clogged injector, or bad cat converter.
First thing to do is check for any obvious vacuum leaks, like a tube or hose loose in the engine compartment. You might get lucky.
Then, if you are a mechanically-inclined DIYer, and are up for a little challenge, disconnect your negative battery cable, get under the car (with it jacked up and blocked, of course) and change out both your upstream and downstream O2 Sensors. Buy Denso (not a random after-market sensor). You can get both of them from RockAuto for around $150.
Now... Before anybody starts screaming at me for "throwing parts at a problem," keep in mind that - at worst - you're out $150, and you have 2 new O2 Sensors installed. And we all know that $150 is spent before you even get the engine shut off at a dealership. Plus, having had the battery cable disconnected, your CEL light will be off. Obviously, if it comes back on, your problem has not been fixed.
Your other alternative is to take it to a dealership or independent shop, and have them diagnose and fix the problem. If you do that, you really don't need any of our help or opinions.
Could the cat have gone bad that fast (6 months) or is it something else?
Yes and most likely the shop that scanned the vehicle did what so many shops do, and that's replace what the codes states instead of checking the system out completely.
You most likely have a bad 02 and a possible bad cat due to their mistake.
I've gotten this code on a Honda CRV before. I was told it could either be the cat or O2 sensor. I replaced the O2 sensor since it was something simple I could do myself and it cleared the code.
Seems like it's the downstream O2 sensor 90% of the time as compared to the one before the cat. conv.
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