My Check Engine light keeps coming on and going off lately. When I'm going down the road, it'll come on for a few seconds and then go off. When I'm sitting idling in park or neutral, it comes on just as the idle kicks up from 900 to 1100. The codes indicate 13 [Oxygen Sensor Circuit Failure] and 35 [Idle Speed Error]. What can I do?

Well 13 [Oxygen Sensor Circuit Failure] and 35 [Idle Speed Error], It seems to be both of these sensors are wornout, time for new parts, I would take a look at the wiring harnesses, As well before replace the sensors. If that checks out good, Then replace the sensors.

Good Luck.

Just a note on code 35 that is specifically for the IAC (idle speed control) IAC valve. Probable issue's are check the idle speed,check ur fuel pressure, and check for a leaking injector and anything in the throttle body.Replace the IAC valve is prob what u will need to do is the bottom line if everything else is good.The O2 sensor is generally good for 50-60 thousand miles but,that is dependent on the cars running condition and issues that may deteriate the part quicker based on that.I would do a new oxygen sensor automatically.