p0171 + p0174 2010 Suburb

[abdullah_Zahra]

RPM fluctuation at idle, though it was a vacuum leak somewhere but the fueltrim values on my OBD scanner looked normal to me! Can the brake booster have anything to do with this? I think mine is going out, plus codes: c0253, c1100 have been found in the EBCM.
What can I check next?

 

[Fless]

Give us an idea of what year, make, model and engine you're working on.

I agree that the fuel trims look okay; adding each bank's ST & LT trims it's within +/- 5%.

Has the throttle body and IAC been cleaned lately?

It has lean codes with those trims? Check upstream O2 sensor activity.