Originally had check engine light so since I was bringing to mechanic for something else anyway I had him check. Said it was a random misfire from o2 sensor but said it didn't say which one. So he reset code. Went a few more hundred miles and got another cel. So I got an obd scanner and showing P1177 Maximum Negative FMFR Correction Fault. Any ideas on cause/fix?

 

My guess is the MAF sensor.

 

This codes relates to ECM activity in terms of correcting a rich or lean fuel mixture. Your particular code is: Maximum Positive Air Mass Flow Rate (AMFR) correction fault. P1179 is the other end of the scale is Maximum Negative AMFR correction fault. It would seem you would have to investigate the reason your fuel mixture is beyond the correction abilities of your ECM. First, make sure you have a clean air filter and replace it if it is time to do so. Next, check for leaking or cracked intake manifold hoses and check for intake manifold leaks by spraying starter fluid around the base of the intake manifold with the engine idling. Finally, check connections to the Mass Air Flow sensor and clean the MAF sensor wire with CRC sensor spray. Beyond these simple steps, the next steps would require removal and cleaning of the throttle body, but in most cases the steps outlined cure the problem. Good luck and check your fuel cap to insure it is on tight.