1997 Legacy 2.2, 212,000 miles

 

Well, it just figures… After running MIL free for over a year, and with my inspection sticker set to expire on August 31, the MIL (aka CEL) came on on my way back to PA from ME last Saturday. Came on about 200 miles from home and stayed on. There was no indication of any actual operational problem with the car. Connected a scanner last night. Good ol’ P0420 (Cat efficiency below threshold or some such thing). From what I believe I have read here in the past, the most likely culprits are the upstream oxygen sensor, an exhaust leak or the catalytic converter itself. Correct? Now, I know I have a small leak at the last joint in the exhaust system but this is in the back of the car at the front of the (final) muffler section. That could not be it, right?

 

Anyway, I cleared the code, the light went off and the scanner says no faults are detected. But, of course, the system is not “ready” so I will not be able to get the car past inspection. Can someone please refresh me as to what it takes to get the system “ready” and how long that might take? If I recall correctly, this can take a long, long time….

 

As always, thanks for any and all comments!

 

Mike V.

[...] Good ol’ P0420 (Cat efficiency below threshold or some such thing). From what I believe I have read here in the past, the most likely culprits are the upstream oxygen sensor, an exhaust leak or the catalytic converter itself. Correct?

Those are likely (but certainly not the only) culprits. See http://www.catalyticconverter.org/news/news_page.cfm?Key=catalytic_converter-&News=120

 

 

Now, I know I have a small leak at the last joint in the exhaust system but this is in the back of the car at the front of the (final) muffler section. That could not be it, right?

That's right, leaks well beyond the downstream (rear) O2 sensor won't cause P0420 to be generated.

 

 

Anyway, I cleared the code, the light went off and the scanner says no faults are detected. But, of course, the system is not “ready” so I will not be able to get the car past inspection. Can someone please refresh me as to what it takes to get the system “ready” and how long that might take? If I recall correctly, this can take a long, long time….

It's usually not too bad with '97 and later models. After the engine is warm, a 10-15 minute run on the highway at constant speed will usually do the trick. See http://endwrench.com/images/pdfs/OBDInfo.pdf .

Thanks for the comments, 99. But, man, unless you have access to the Bonneville Salt Flats how can you run at any speed for ten minutes without changing the throttle angle?!?

 

This is my wife's car. I cleared the light on Tuesday and it has not yet returned with her 'round town driving (and a few miles with a kid on his learner's permit:eek:). I'll check the readiness status tonight. If it is not ready by the weekend, I'll try to get it on the highway and run at 55 mph while moving the throttle as little as possible.

 

Mike V.

Thanks for the comments, 99. But, man, unless you have access to the Bonneville Salt Flats how can you run at any speed for ten minutes without changing the throttle angle?!?

You're welcome, Mike. The EndWrench article describes the way to get readiness as quickly as possible, but it can certainly be done under less-ideal conditions. You might even find all the monitors ready when you next check. If you do a highway run, mainly try to minimize throttle movement.

 

Anyone have a 4-wheel chassis dynamometer at their disposal?

Chaecked the readiness status last night and there are still three incomplete tests (I think they are oxygen sensor, catylst and evap system, something like that). So I guess I'll have to take this thing on the highway if I want to get it inspected last week. Hopefully it won't reset the error again by that time!

Have the monitors on the car tested as ready before this? The 1996 (and some early-production 1997) Subarus had a problem where the monitors are set to ''not ready'' (incomplete) each time the ignition is turned off. It's known, and such cars are exempt from the requirement.

 

See appendix D of http://www.epa.gov/OMS/regs/im/obd/r01015.pdf

Also see http://www.ultimatesubaru.org/forum/showthread.php?t=100936 and links within it.

Oh yeah, I remember reading about that a while back. But, no, my car does not have that issue. EVENTUALLY, it will show all tests as complete (and stay that way) but if I remember correctly, this has taken many miles and many days (weeks?) in the past.

 

Thanks again,

Mike

Mike, I don't know how reasonable (or unreasonable!) your inspection process is, but some jurisdictions will give you a week or two to get your car in compliance if they can't pass you.

 

Maybe it's worthwhile to go talk to them or start the testing procedure anyway.

 

Good luck.

PA allows inspection to proceed with two monitors not ready on 1996-2000 cars. See http://www.drivecleanpa.state.pa.us/drivecleanpa/docs/readiness.pdf

I found this procedure a couple of years ago on this site or via Google. I tried this and it worked.

 

"Subaru recommends the following conditions and drive cycle to get the monitors on its vehicles completed in the shortest amount of time:

 

1. Make sure the fuel tank is between one-quarter and three-quarters full; half a tank is ideal.

 

2. Start the engine and immediately drive the vehicle for at least 15 minutes at a speed greater than 50 mph. During the warmup, try to avoid sudden acceleration, hard braking and/or lane changes.

 

3. Drive the vehicle at a steady 55 mph for three more minutes. During this stage of the drive cycle, it's crucial that you keep throttle angle changes to a minimum.

 

4. Bring the vehicle hack to the shop, hook up the scan tool and look at the status of the readiness monitors. Repeat the drive cycle, if necessary."

Well, as I was ruuning down the highway trying despartely to hold a constant throttle position the MIL illuminated again! Oh well. So I cleared the code again (P0420) and just used the car normally for a few days. Thanks for the reminder, 99, about PA allowing up to two incomplete tests! I totally forgot about that loophole. Anyway, after a few days, the scanner showed only two incomplete tests so I got the car inspected yesterday. Good for another year! If the code gets set again I think I'll pick up a couple of spark plug anti-foul fittings....

 

Thanks guys.

 

Miike V.