[New2Subies]

Hey everybody, I drive a 02 MT forester and I recently got the oil changed then drove like 8 mi to a friends house stayed awhile then left filled up with gas and left town and probably only one or two miles on the highway my check engine light came on. I figure I didn't tighten the the fuel cap tight enough or something b/c it came on shortly after filling up, and when I tried to fill it up it clicked off at 11.5 when I was bone dry which was weird but probably just something with that particular pump. Anyways I took it to autozone today to get them to read the code and the guy got no reading and told me to check the fuses and left, wasn't a very friendly guy. Anyways I checked every fuse that I thought could be related and could check, I don't know how to check the non- transparent ones under the hood, and they were fine what do I do now? Thanks in advance for helping me out again.

 

[rsay777]

well, if the CEL is still on but no codes read then I would clear the CEL buy disconnecting the negative battery cable and then depressing the brake pedal (drains voltage)

reconnect neg bat cable and see if the CEL remains off.

 

[ddavidv]

I think you need to have the code checked again by someone who knows how to use a scan tool. I don't see how a fuse would have anything to do with it.

 

[paulv]

I think you need to have the code checked again by someone who knows how to use a scan tool. I don't see how a fuse would have anything to do with it.

:lol: You've had that same experience at AZ? That's why I just go to them to buy oil!!

Regards,
paul...

 

[Papa_D]

I think you need to have the code checked again by someone who knows how to use a scan tool. I don't see how a fuse would have anything to do with it.

Is there really anything to reading one because I was under the impression that you just plugged it in and there either was or wasn't a code?

 

[paulv]

Is there really anything to reading one because I was under the impression that you just plugged it in and there either was or wasn't a code?

There's a lot more to it. When a test fails on the first drive cycle, the PCM will set a pending code (these can be read with a scanner). If the issue still exists at the second drive cycle, then the CEL is set on. This works for what are called "non-continuous monitors" (EGR, EVAP, etc). The other tests are continuous (misfires, air/fuel, etc) and will set the CEL immediately within one drive cycle.

So ddavidv was suggesting that someone who knows how to use a scanner would be knowledgeable of all this (which leaves out most of the people who work at AZ) and could tell you that there's a pending code (assuming it exists).

Also, if you're lucky enough to find someone at these parts stores who does understand, and you have the CEL on, ask them to tell you a few values from the freeze frame data (assuming the scanner they have can read FF data) -- these are short term fuel trim (STFT) and long term fuel trim (LTFT) for both cylinder banks (these values can be + or -). These are good to know when troubleshooting driveability problems and especially misfires to determine if the misfire is occurring from an ignition or air/fuel or mechanical/other sensor problems. And then post those values here so we can help.

Regards,
paul...

 

[Papa_D]

There's a lot more to it. When a test fails on the first drive cycle, the PCM will set a pending code (these can be read with a scanner). If the issue still exists at the second drive cycle, then the CEL is set on. This works for what are called "non-continuous monitors" (EGR, EVAP, etc). The other tests are continuous (misfires, air/fuel, etc) and will set the CEL immediately within one drive cycle.

So ddavidv was suggesting that someone who knows how to use a scanner would be knowledgeable of all this (which leaves out most of the people who work at AZ) and could tell you that there's a pending code (assuming it exists).

Also, if you're lucky enough to find someone at these parts stores who does understand, and you have the CEL on, ask them to tell you a few values from the freeze frame data (assuming the scanner they have can read FF data) -- these are short term fuel trim (STFT) and long term fuel trim (LTFT) for both cylinder banks (these values can be + or -). These are good to know when troubleshooting driveability problems and especially misfires to determine if the misfire is occurring from an ignition or air/fuel or mechanical/other sensor problems. And then post those values here so we can help.

Regards,
paul...

Thanks for the information, I was aware that some codes disappeared over time or due to key cycles and other factors but was unaware that if there was a warning light that the code was not easily retrievable and certainly knowing how to retrieve the other data helps as well so I suppose I will get my own scanner and learn how to use it properly so as not to have to rely on the average AZ worker for valuable data.

 

[paulv]

Thanks for the information, I was aware that some codes disappeared over time or due to key cycles and other factors but was unaware that if there was a warning light that the code was not easily retrievable and certainly knowing how to retrieve the other data helps as well so I suppose I will get my own scanner and learn how to use it properly so as not to have to rely on the average AZ worker for valuable data.

You'll be looking at around $100 for something good that gives you what I mentioned (in a hand-held unit).

Regards,
paul...

 

[ddavidv]

I wonder about the training they do (or don't) get at AZ. Something as simple as plugging the scan tool in but not turning the key to 'on' may baffle the average mouth-breather they hire. They are NOT hard to use, but then neither is jump starting a car and people do that wrong every day.

 

[New2Subies]

So i went to a different az today, and they told me it was either the catalytic converter or an o2 sensor. Then someone suggested after a long drive I climb under it and look to see if the catalytic converter is hot. Does this sound right, is it a bad idea to risk a 120 mi drive this weekend? The I always thought the exhaust/muffler sounded in bad shape. could this be the catalytic converter?

 

[jgrote]

Did he tell you what the code was? If it's a P0420, fix it when you get back. It'll be a bad rear O2 sensor.

 

[goshring]

What bothers me here is the poor customer service. When I go somewhere and they act like they are to busy to care about helping me, then I will not care enough to spend my hard earned money there. If some guy at Autozone is to busy to do his job, mob then go to another store that wants your business. As far as reading codes goes, I thought I had it figured out pretty good until paulv started in on his explanation. I guess I need to read up and learn a little bit/lot (lol) more about using one...thanks paulv. Anyway, you really need to actually get the codes its trowing so someone here can help point you in the right direction. If you have a cat going bad, your car will start to run real rough, especially up hill (in most cases). You could get under the car when its cool and gently bang (is that an oxymoron?) on the cat an listen for rattling and debris moving around. Your cat will be hot when in use regardless of its working condition so I am not sure what he was telling you to do. Before spending any money though I would find someplace that wants your business and will show you the codes and give you good customer service. And if you were so inclined, you could buy a pretty good scan tool for $100.00 to $150.00 Good luck and keep us up to date.

Kenny