Question

2004 Cadillac DeVille with engine code P0171 & P0174. what are these codes??

Answer 1

Dirty air filter of faulty air flow sensor are common causes for the P0174 code of the problem.

P0171 - System Too Lean Bank 1

Possible causes:

- Intake air leaks 
- Faulty front heated oxygen sensor 
- Ignition misfiring 
- Faulty fuel injectors 
- Exhaust gas leaks 
- Incorrect fuel pressure 
- Lack of fuel 
- Faulty Mass Air Flow (MAF) sensor 
- Incorrect Positive Crankcase Ventilation (PCV) hose connection

P0174 - System Too Lean Bank 2

Possible causes:

- Intake air leaks 

- Faulty front heated oxygen sensor 
- Ignition misfiring 
- Faulty fuel injectors 
- Exhaust gas leaks 
- Incorrect fuel pressure 
- Lack of fuel 
- Faulty Mass Air Flow (MAF) sensor 
- Incorrect Positive Crankcase Ventilation (PCV) hose connection