i got 2 engine codes today, one is p0400 which is the egr valve and the other is p0136 which is o2 sensor.
now on the egr valve i cleaned out throttle body of all carbon, the light is still on after that..do i replace the egr now?
and for the o2 sensor, how do i know if its pre cat or after cat sensor?
thanks for any help
jonny