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#16848 of 19283 help with Check Engine ight codes
May 31, 2006 (5:34 pm)
Codes: P1443 Evaporative emission control system vent control function problem
P0420 Catalyst System Efficiency Below Threshold (Bank 1)
Year/Make/Model: 2001 Subaru Forester
Mileage: 117,500 mostly highway miles
Fix for problem: nothing yet.
Hi, all. Need your advice on the above codes that have showed up on my Subie, according to the free diagnostic Advanced Auto Parts ran for me this morning. Here's the relevant background:
For a few weeks now, i've noticed the Check Engine light come on --steady, never blinking--most noticeably after filling up my tank with gas. It'll stay on for several days and then when I fill up again or soon after, it will disappear for 30 miles or so. It usually clears on its own after 10 or so startups. But it's frustrating as hell and I don't know if I have a reason to worry or not. by the way, I don't smell anything unusual at all (someone on this forum with a P0420 reported a smell of rotten eggs). And I've noticed no performance reduction at all. Still averaging 27mpg!
When I fill up with gas I try to make sure I screw the gas cap all the way on till it clicks 3 times. Admittedly I do top off, and I've read on this forum that that's not a good idea. I'll make that change immediately. My fluid levels are all okay, I checked that to rule out anything else (oil, washer, radiator).
My questions to you:
1. What does it tell you that these 2 codes appear together?
2. What would you do next if you were me?
Thanks very much for reading this far.
#16849 of 19283 Re: help with Check Engine ight codes [dankorte]
Jun 01, 2006 (6:36 am)
Dan, you probably have two problems. I'm not going to answer #1 because they are unrelated.
P1443 is probably due to topping off, but if that doesn't solve it you should get a new gas cap. Some have had luck with various aftermarket ones, like a Stant locking cap for example, or you couldn't go wrong buying a new one from a dealer. Rarely does the evaporative canister itself go bad, but that is an outside shot. Try the cap first of course, since it's cheap.
P0420 is usually a sign that the catalyst is wearing out or that you have an exhaust leak. Both are possible at your mileage, and I'd check for the exhaust leak yourself-- you will be able to hear a strange puffing noise down there if you have the car idling and listen beneath it. (Of course, use normal cautions when working under a car, such as blocking the wheels and jacking it appropriately with a jackstand if you need clearance.) There is a second oxygen sensor whose function is to generate this code and it doesn't typically affect driveability but it is annoying seeing that orange malfunction indicator light. If you don't find an exhaust leak, I'd price out a new catalyst and second oxygen sensor, then consider doing both. It should be cheaper than the primary o2 sensor because it is less sophisticated.
#16850 of 19283 Re: help with Check Engine ight codes [locke2c]
Jun 01, 2006 (7:40 am)
Colin, thank you very much for the insight and advice. I appreciate it. Are you sure the two error codes are unrelated, though? Doesn't it stand to reason that 1443 could actually cause the o2 sensor to kick out the 0420 code?
#16851 of 19283 Re: help with Check Engine ight codes [dankorte]
Jun 01, 2006 (7:52 am)
nope, they are totally unrelated systems. your evaporative canister is a black plastic box near the gas tank. it has nothing to do with the second oxygen sensor that is checking catalyst efficiency.
#16852 of 19283 Re: help with Check Engine ight codes [dankorte]
Jun 01, 2006 (8:40 am)
According to my shop manual, P1443 (evaporative emission control system vent control function problem) deals mainly with the drain valve & filter attached to the canister, and associated hoses that route collected fuel between the collection canister, the filler tube, injector rails and the fuel tank.
To begin with, I would stop fueling as soon as the pump kicks out. There are pickup points & returns on the filler tube itself, and you don't want liquid fuel sitting up against them. A small valving problem there could be flooding the canister, drain valve & filter. Maybe it will dry out and recover, maybe it is now damaged. Only time will tell.
Jun 01, 2006 (11:02 am)
Definitely stop topping off, ASAP.
You can check the canister to see if any of the hoses are loose or leaking. It's a sealed system so any leak with trigger a check-engine light.
Here's a photo of mine, when I was installing the hitch. On a Forester, it's on the passenger side rear, just in front of that tow hook.
#16854 of 19283 Trailer connection?
Jun 03, 2006 (6:52 am)
I'm contemplating wiring my OB for towing a small utility trailer. Is there a connection point for a wiring harness somewhere, or is it a splice-and-dice proposition?
(who hasn't forgotten this place, but kid's baseball is presently ruling my life!)
#16855 of 19283 Re: Trailer connection? [hammerhead]
Jun 05, 2006 (8:55 am)
OB and Forester are pre-wired. If you get the OE wiring harness it's plug and play, easy as cake.
#16856 of 19283 Re: Trailer connection? [ateixeira]
Jun 06, 2006 (10:30 am)
Thanks, juice - I'll dig around for it. One complication may be the wiring was modified when we pulled the OB with the motorhome, so the brake lights would show. may just bite the bullet & get a shop to do it right.
#16857 of 19283 Re: help with Check Engine Light codes
Jun 09, 2006 (6:45 am)
Juice, Steve, Colin- thanks for your help and advice.
I just wanted to post an update.
I stopped my practice of topping off the fuel, and thought I had the problem licked. The CEL cleared a few days after filling up, and stayed off for a few days, or roughly 75 miles. Then it came back on.
So now that it's on again, this time I have to deal with it. So I'll take it in and give my mechanic a printout of your suggestions. That way at least he won't waste time looking in the wrong areas.
Thanks again to all. will continue to keep you posted.