Problem with 35d x5 p0112 and p0675

[2011diesel]

Hey guys, I've been having a check engine light on my x5 for awhile now, it's showing 2 codes which are p0112 intake air temperature sensor and p0675 cylinder 5 glow plug curcuit. Now the x5 runs fine, nothing noticeable. I did just replaced the intake air temperature sensor, and replaced the air filter (it was dirty) and cleaned the MAF sensor, and both codes are still there. On Bosch code reader says they are permanent, trying to erase them, and the check engine light turns off, until the car is restarted and it's back on. I did a lot of research already, before I posted this, and no luck. Please let me know where to look, I can't afford to pay $190 to BMW for diagnostics just yet, but will have to if nothing else can be done. Also to note, I took the car on a long trip from WA to CA, and my mpg was 25. I'm not sure if that's normal or if it's suppose to be more. The car has power, I didn't notice any power reduction.