P0171 2001 Ford Windstar -

Question

I need to replace the o2 sensor on 2001 windstar. is bank 1 front or back on engine?

Answer 1

P0171 Fuel trim system lean Bank 1

P0174 Fuel trim system lean Bank 2

Neither one of the 02 sensor will solve this code condition, what you have is mostly  related to a vacuum leak condition. Or the MAF (Mass airflow) not reporting the correct condition. The 02 sensor are just reporting the situation.

 On this Ford a vacuum leak was found here, its poor connection here cause a lean code condition for both side of the Banks. To prevent it from comming out a zip tie was use to hold it in place.