Avalanche OBD11 codes question

[Gordo]

I have been getting both PO171 and 174 codes on my 02 Avalanche 5.3 for a while now. Just been resetting the light but thought I better find and fix the problem. Am I looking at a bad o2 sensor here?

Thanks!

 

[Texan]

I have been getting both PO171 and 174 codes on my 02 Avalanche 5.3 for a while now. Just been resetting the light but thought I better find and fix the problem. Am I looking at a bad o2 sensor here?

Thanks!

P0171 System too lean (Bank 1) P0174 System too lean (Bank 2)

Could be vacuum leak, low fuel pressure, fuel filter.
Really need to run a scanner and see the results.