GMC Repair: 1999 gmc suburban, fuel pressure regulator, o2 sensors

Question
System to lean bank 1 and 2 came on the scanner and code po171 and po174 what does this mean?

Answer
Hi
It means that both banks (sides) are running lean. That is either too much air or not enough fuel. The O2 Sensors are indicating lean condition and they cannot adjust it out.
Possible causes - Vacuum leak, faulty MAF sensor, faulty O2 sensors, very plugged fuel filter, weak fuel pump, internal fuel leak (leaking injectors), faulty Fuel pressure regulator. These are all items that could be cause plus ANYTHING that will cause a lean condition.
Hope this helps
Just advice from experience
Good Luck
Pawl