Got my scan tool, found my problem, now what?

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demarpaint

demarpaint

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As always thanks in advance. My Jeep had a CEL light, I hooked my scanner found P0456, and what appears to be something that I upset taking down the spare tire to put air in it. CEL is now out but the P0456 code is stored. My instructions say to erase DTC I must do a DRIVE CYCLE for the vehicle under test. Refer to vehicles service manual, which I don't have.

It is an 08 Jeep Liberty, how would I do this? Scanner is a Equus 3160.

Again thanks!
 
The car has to relearn certain parameters for the idle , mixture, and ignition advance.
It has a short term and long term memory.
It can take quite a few cold/hot cycles and starts to eliminate the 'not emission test ready' hidden code.
This is there so people don't clear their codes and drive through the test area immediately afterward.

Anyway, relearning is normal and just drive it.
You may note anomalies that get better and better.
Don't forget to use the AC - all sorts of other stuff for the idle will be relearned.
 
Thanks guys, I found what I think was the problem and corrected it, CEL is out the Jeep is running great. I've driven over 100 miles and the code is stored when I check with the scanner. The CEL is still out.

Driving will remove the code as long as the CEL stays off and the problem is no longer present? Is there a way of removing the stored code without all the driving and on off cycles? Or do I leave well enough alone?

Thanks
 
Let me re-phrase my question. I'm "fairly" certain the P0456 code issue has been resolved. The CEL light is off, but the code is stored. How do I remove the stored code? Vehicle in question is a 2008 Jeep Liberty.

Thanks!
 
It really is not a stored code. All this means is that the drive cycle is not complete for this concern. The PCM does a series of tests during driving to check the integrity of the evap emission system. You run into the same problem with catalytic converters. When all of the codes are cleared you have something that tells you (or the inspection/emission station) that a code was cleared and the vehicle has not been driven enough to verify the repair.

If the vehicle is fixed, the code will be cleared when a specific drive cycle is complete.
 
Thanks for clearing that up!

What happens in the event a part like an 02 sensor needed to be replaced? How would you clear the codes for that?
 
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Originally Posted By: demarpaint
Thanks for clearing that up!

What happens in the event a part like an 02 sensor needed to be replaced? How would you clear the codes for that?



My understanding is that you don't clear the codes. It should go out by itself. Again, it will store in memory that the code was set, but after a certain amount of key on/off cycles, the stored code will also clear from memory.
 
Thanks, now what happens if you get a CEL a few days before a state inspection, pull a code replace the part. CEL is off you go for your inspection and they find a code stored in memory? Will the vehicle pass? Or do you need to prove you replaced the part?

Sorry for all the questions, this is my first vehicle with OBD2, and I'm trying to learn about it.
 
I would clear the codes and then go through the drive cycle until all the readyness monitors show as complete. If that happens and no codes are stored, the problem is fixed.

Generally, though, if the CEL goes off on it's own then the code is no longer stored in memory.

Also, sometimes after you clear the codes it'll complete the readyness tests a lot sooner than it otherwise would.
 
Quote:
I would clear the codes and then go through the drive cycle until all the readyness monitors show as complete. If that happens and no codes are stored, the problem is fixed.


+1 ..keep in mind that a drive cycle isn't JUST clearing the code and driving. It's typically what's defined as a good trip which may require a cold start.
 
I'll keep driving and see, the light is off, but the P0456 code shows when the reader is hooked up.
 
Originally Posted By: demarpaint
Thanks, now what happens if you get a CEL a few days before a state inspection, pull a code replace the part. CEL is off you go for your inspection and they find a code stored in memory? Will the vehicle pass? Or do you need to prove you replaced the part?




That will depend on the laws in your state. In NJ, they will fail you for a stored code even if the CEL is off. Happened to me.
 
Originally Posted By: brianl703
What readyness tests does your reader say are not complete?


I'll have to check again tomorrow. I just got the scanner and am learning how to use it.



Originally Posted By: ron917
Originally Posted By: demarpaint
Thanks, now what happens if you get a CEL a few days before a state inspection, pull a code replace the part. CEL is off you go for your inspection and they find a code stored in memory? Will the vehicle pass? Or do you need to prove you replaced the part?




That will depend on the laws in your state. In NJ, they will fail you for a stored code even if the CEL is off. Happened to me.


NY will fail you for a stored code too, which is why I asked the question. I plan on hooking up the scanner before NYS inspection, fortunately I don't have an inspection in this case until December. But for the sake of argument lets say I get a CEL for an 02 sensor replace it and clear codes. I'm guessing there would still be a stored code, and I'd fail even if the repair was made by me?
 
IDK about a stored code. I do know that 1 emissions test can be not passed, and the vehicle will pass.

If the PCM cleared the code by itself, it may erase it completely. Otherwise, all bets are off.
 
In WI, if you've cleared your CEL, but not finished the drive cycle, they just run the dyno and sniff the tailpipe. Typically only happens after you replace something prior to your emissions test and the car hasn't had enough time to be happy.
 
I ran the test again, P0456 is a stored code CEL is not out, I cleared the code from memory. Probably a stupid thing to do, but it is done.

I have a yellow light, vs green. There are no pending codes. From what I can tell from reading the book is this is caused by "Monitors that have not run their diagnostic testing".

Do I continue with the drive cycle, and recheck at a later date to see if I get the green light? Dealer is backed up with work, so it is just as well. I made an online appointment never got a confirmation, so they can't see me for another 2 weeks.
 
Quote:

NY will fail you for a stored code too, which is why I asked the question. I plan on hooking up the scanner before NYS inspection, fortunately I don't have an inspection in this case until December. But for the sake of argument lets say I get a CEL for an 02 sensor replace it and clear codes. I'm guessing there would still be a stored code, and I'd fail even if the repair was made by me?


When you clear the codes, the stored codes are also cleared.

But - all of the monitors (self tests run by your ECU) are reset when you clear the codes. You won't pass emissions inspection until your car is driven enough for the monitors to complete the self tests. The factory service manual for your car will have the details, but usually a few days of normal driving will do it.

Your scan tool should tell you if any monitors are still pending - mine does.

So the way to proceed if you get an O2 sensor code is to fix it, clear the codes, drive normally for a week, and use your scan tool to check if the tests are complete. Then go for your inspection.

In NJ, I think you are allowed to have one monitor pending.

More info here: http://www.aa1car.com/library/2004/ic50452.htm
 
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