P0170 is fuel trim Bank 1 and P0171 is system too lean Bank 1
Lean fuel condition could be caused by one of the following below:
1. Vacuum leaks
2. EGR and PCV valve.
3. Low fuel pressure.
4. Dirty fuel injectors.
5. Mass Air Flow Sensor.
6. Oxygen sensor
Tuesday, May 4th, 2010 AT 4:18 PM