My 97 xj threw a code a few weeks ago. After a few days of driving the CEL shutoff. While picking up a fuel pump yesterday I decided to get my computer scanned even though the CEL wasn't on anymore just to see if it would show the last code. The guy at the parts store told me if there's no light there won't be a code to read. I told him I'm not sure that he's right about that and wanted to try scanning it anyway. He agreed, and it then became clear while watching him hook up the scanner he has not had much experience doing this. At the bottom of the results screen it said "no codes found" but above that was a code for an O2 sensor issue. Unfortunately I didn't get to read it because the guy quickly turned off the scanner and said "told ya so."

So my question...does the computer automatically clear the code if the issue is resolved or are they stored for a period of time?

 

Avoid taking it to that guy again. Yes, the PCM can store codes that don't light the CEL. Do yourself a favor and hit up amazon and get an OBDII bluetooth dongle for around $10 and the torque app for $5. Not a professional tool, but it will do everything you need it to and then some.

 

Thanks, I will look into that bluetooth OBDII thing...been wanting my own scanner.

I usually don't go to that place but my usual auto parts store had several people waiting in line when I picked up my ordered fuel pump assembly, so I decided to go to a place on the way outta town that is always dead, thinking they could at least handle reading the PCM. I should have walked away when I said I wanted an OBDII diagnostic test ran and he said "You mean the check engine light thing?"

 

OBDII scanners: http://www.amazon.com/s/ref=nb_sb_ss...bd%2Caps%2C384


Here is the one I have but I paid @ $12 for mine. It reads the codes and that is what I needed it for. It comes with a disk but I suggest the Torque Pro App for your phone:

This is the Torque App on Google Play: https://play.google.com/store/apps/d...g.prowl.torque