What does it mean when the Check Engine light comes on and goes off?

I got a check engine light come on a couple of days back, and it was there for less than a day before it went blank again. I have a car code scanner, and it came back as P0325 (Knock Sensor problem). Now the fact that the light went out again, does it mean that the knock sensor fixed itself? I checked the code again, and it still shows the same code, but that's probably just because it records the last problem.

I know that the Check Engine light sometimes automatically goes out after a certain number of days, but I thought that would be after 3 days or so.

Should I clear the code, and see if it recurs?

Yousuf Khan

Reply to
Yousuf Khan
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It means the problem is being detected intermittently by the ECU. When the condition isn't seen for a few driving cycles, the light will go out but the code remains in memory for retrieval. If the problem is detected again, the light will come back on. Most likely the sensor itself is the problem, but it could also be a wiring fault. The knock sensor is not an expensive part and is fairly simple to replace.

Reply to
mulder

I kind of figured it isn't too hard to fix, as the dealer is only quoting 45 minutes for labor on this. However, he's also quoting $160 for the part! I figure if I have to pay that much for the part, I might as well save on the labor by doing it myself.

Is that as good a price as I'm going to get for that part? It's in Canadian dollars, but the US and Canadian bucks are pretty much the same these days.

Yousuf Khan

Reply to
Yousuf Khan

seems high. Regardless, I always price stuff with Jamie at

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and then decide. Sometimes you can get a local dealer to match online parts. (this worked for my springs and got close enough on my SS braided brake lines to spend the money locally. Other stuff, I bought (engine undercover, Roki oil filters, STI windshield wipers for my WRX, etc.) from them. There 'may' be a Bosch or other aftermarket part - but folks have had bad luck with non- OEM for other sensors, knck sensor might be OK aftermarket. YMMV

Carl

1 Lucky Texan
Reply to
1 Lucky Texan

This is quite common. And yea, clear the code. It will most likely re-occur, but as long as the CEL is goin' away after a day or two, I wouldn't worry about it. If it starts staying on for longer periods. you'll want to replace the sensor; your gas mileage will suffer otherwise. I'd suggest getting one at a salvage yard; probably $30 or so. There is a way to test one with an ohmmeter. I don't recall the exact procedure, but sou should be able to find it on-line, and the yard guys should know in any event. It's about a 10 minute job to swap one of these; takes a 12mm socket, an ~4 inch extension, a ratchet, and an ice pick or similar to work the connector. Let me know if you need details.

ByeBye! S.

Steve Jernigan KG0MB Laboratory Manager Microelectronics Research University of Colorado (719) 262-3101

Reply to
S

Unfortunately, those guys don't ship to Canada (I've asked already). So it's not certain that the dealer is going to try to match the online price, if they know that these guys won't be shipping into here.

Yousuf Khan

Reply to
Yousuf Khan

Thanks Steve, I found an online instruction page with pictures showing where the knock sensor is and what it looks like (at least for a Legacy, might be the same for an Outback).

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Yousuf Khan

Reply to
Yousuf Khan

De nada.

Legacy, Impreza, SOHC 2.5, DOHC 2,5 all pretty much the same knock sensor arrangement; good ol' Subaru. Some models, you may have to pull off more of the air intake plastic to get at it, that's about all. I'm lazy, and usually just take off everything as a unit, all the way to the throttle body; that way everything stays clean and more or less in alignment.

When you put it back on, be sure to re-connect all of the PCV hoses, and be careful that the boot at the throttle body doesn't get pinched under.

This makes a good time to install a fresh air filter, and PCV valve if you're so inclined.

Have fun!

ByeBye! S. Steve Jernigan KG0MB Laboratory Manager Microelectronics Research University of Colorado (719) 262-3101

Reply to
S

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