To try to clear a c.e.l. does it matter which battery cable you take off. I think i just left gas cap loose.

 

Normally, you Always Remove the (-) NEG Battery cable first, no matter what your problem is:

How to Disconnect a Car Battery

Yes, it is possible you can cause a CEL code with a loose gas cap.
Years ago, I had a older Chrysler van. I lost my original gas cap and replace it with a auto store bought cap.
It cause a CEL code and Smog Check Failure. I replaced it with a OEM gas cap and Problem Solved.

 

To clarify someone told me to leave one hooked up and only remove the other. Thanks

 

So my son gave me a pt tools scan tool which I tried to read my stored codes and erase them but I couldnt get it to work right. So I went the next morning to local mechanic who scanned it with his snap on scan tool. Said it had a 1600 series code that had to do with a theft deterrant module, not to worry about it and erased the stored code. My plan is to by a $120.00 scan tool from advance for the next time this may happen.

 

Well my CEL came back on and my performance tools scanner wont work. Any one know the best budget scanner from advance or autozone?

 

So ran down to Autozone and had them scan and clear the code, downstream 02 sensor. 10 min job.