comes on and goes away and comes on and goes away anyone know why?

 

Wrong section but have you even tried pulling the code? That would be the first step you need to find out why it's coming up in the first place

 

Most likely a "pending" code resetting for some reason. Take it to Pep boys, Reilly's, etc. They can use a scan tool and get the pending code in question. It hasn't hard set so request they pull pending codes. It'll be free as they will want to sell you fix it parts. Post the code and folks here can help.

Utah

 

You could also buy an obd2 scanner to save time going to all these places that want to sell you a "quick fix". Pretty annoying sometimes


btw


"When a test fails, the check engine light may come on. We start a new drive cycle and if the test that turned the light on does not run the MIL may turn off. This does not suggest we have solved the problem. The light is off because the PCM moves the information about the fault to history, and continues checking the problem. The next time the PCM runs the failed test, the light comes back on."

source: http://www.agcoauto.com/content/news/p2_articleid/206

 

My car is doing the same thing now. 95k miles on it and never had a CEL until 2 weeks ago when I put a test pipe on it (even though it has the anti-fouler welded on). If your car has a test pipe/HFC/messed up catalytic converter then that is possibly what is causing it. As others already said, take it somewhere and pull the code to know for sure. I personally don't care that mine comes and goes since the CEL for secondary o2 sensor doesn't affect drive-ability.