I am getting two DTC's on my 2002 X5 4.4i with 65K miles, P1159 & P1161. Both are fuel trim codes but the P1161 bank 2 code also reads " oil temp sensor". I replaced the Air mass meter as a first guess, and reset the codes and the light stayed off for about 50mi. Now it is back on again with the same two codes. Where should I turn next.
This sounds like a possible reprogramming issue. The faults may indicate the need to go to someone with a GT-1 so that the faults can be verified with the BMW software and if reprogramming is called for, that can be performed. This may also indicate an intake manifold air leak or the need to replace the PCV plate at the rear of the plenum. The part # for the plate is 11-61-7-508-541
I would also replace the valley pan due to the mileage (part #11-14-1-742-042) and the throttle plate o-ring and the intake manifold profile gaskets #'s 11-61-1-729-727 & 11-61-1-729-728. Also closely inspect both valve cover gaskets and replace if seepage is present. Send me a PM and I will talk you through the process. Good luck and keep in touch!