CEL turned off.

[mikekerstetter]

I have a 2000 OBW with the 2.5L and AT. I had a CEL which was (P0420 maybe?) for 'limits below threshold in bank 1' cat warning light. I had it reset three times since I bought it a month ago. Three mechanics told me to just ignore it, including a local shop that sells and services nothing but used Suby's. But what I was told by the place where I bought it is that it wouldn't go out on it's own, that it had to be manually reset. Tonight I noticed it was off. It was on this morning when I drove it. I thought maybe the bulb burned out. But when I start the car the CEL illuminates and then goes out just like all the other warning lights. This light has been on constantly for the last three weeks, the last time it was reset when I had the oil changed. So, what's everyone else's experience with this? If you have it, does it go off by itself, then come back on later? Or do you have to have it reset manually with the code checker? I'm confused.

[plain OM]

In many cases, the CEL will be turned off if the problem isn't detected for a number of consecutive driving cycles, often three.

So, for example, let's say that while driving a problem is detected and the CEL goes on. Then during the next drive no problem is detected, but the light remains on. On the next two drives, the same. (So three drives with no symptom.) Then on the subsequent drive, the light goes out normally after start up because in the previous three drives no problem was detected.

If, however, a fault is detected in any one of the three driving cycles, the count starts over again. So if the fault is intermittent and appears every three drives, the light will always be on (unless it is manually reset).

Even though the light might go out after three good driving cycles, the code is stored in memory, usually for up to 40 driving cycles, so it can still be read.

[mikekerstetter]

That was short lived. Came back on this morning as I was driving to Walmart.

[pitweasel]

Mine HAD that code for years. Once every few months, it would turn off for a day or two (thank god this happened right at inspection time two years in a row). Finally, I found someone at Autozone who was willing to clear it out to see if it would come back. Of the four codes that were present, only one came back - and that one wasn't it (P0325 stayed).

So, buying an OBD-II reader with an erase function might be a good way to go. Another thing I've noticed: even after replacing my badly damaged knock sensor, the CEL still comes on from time to time. But after disconnecting the battery several times (I had to replace a bulb), the CEL was off again for weeks.

You can get a fairly well-reviewed reader from Amazon for $20 -

Amazon.com: Autel MaxiScan MS300 CAN OBD-II Scan Tool: Automotive

Amazon.com: Autel MaxiScan MS300 CAN OBD-II Scan Tool: Automotive

[mikekerstetter]

Thanks for the tip. Mines on it way!!

[mikekerstetter]

On another thread I found the advice to register on My.Subaru Cookie Test Page (<~ don't know why it shows up that way, it's the link to mysubaru.com and it will take you there) and register my vehicle to find open recalls for it. It turns out that there are two open recalls that were never done, one of them being the front O2 sensor (the P0420 code?), the other being a rear suspension corrosion recall. There was even a link to schedule an appointment with a dealer to have them completed. So, I'm waiting for a call from their service department.

[pitweasel]

Originally Posted by mikekerstetter

Thanks for the tip. Mines on it way!!

Just ordered one myself, too! When I went to give you a link before, I was going to post one that was $45 - then this one showed up on the front page of my search for the first time. Gave it a look and decided to grab one.

[mikekerstetter]

Originally Posted by pitweasel

Mine HAD that code for years. Once every few months, it would turn off for a day or two (thank god this happened right at inspection time two years in a row).

Fortunately I am not subject to an emissions inspection. All they look for here is a visual to ensure nothing in the emissions system was removed or altered. One County over (actually less than 2 miles from my house) is a different story.

[mikekerstetter]

Originally Posted by pitweasel

Just ordered one myself, too! When I went to give you a link before, I was going to post one that was $45 - then this one showed up on the front page of my search for the first time. Gave it a look and decided to grab one.

I got my scanner in the mail today. Hooked it up as instructed and it showed the P0420 code. I cleared it by following the directions. For a $25.39 total cost, it works great. I'm VERY happy with this purchase.

[pitweasel]

You got yours already? Did you pick one day shipping or something? I ordered mine with Prime, and it's not scheduled to get here until Tuesday!

Glad to hear it seems to be working for you sometime. Just don't go celebrating yet...that light isn't necessarily gone for good