Contour Enthusiasts Group Archives Forums General Troubleshooting PO171 Code help

I had my car checked out today at checker and the reader came up with PO172 (Bank One) What does this mean? My car is supposably running lean and feels like it, is it a bad o2 sensor maybe? Any help would be appreciated.

On a V-6 this is the O2 sensor screwed into the rear exhaust manifold between the engine and the firewall.

On the I-4 this is the O2 sensor screwed into the exhaust manifold between the engine and the radiator.

On the I-4 it could also be running lean in general due to a dirty MAF, vacuum leak, or low fuel pressure.

It would really help if you could tell us the year and engine.

Most of the time, this code is cause by a vacuum leak. Check for a hissing sound in the engine bay. Or use the carb cleaner spray method (spray in the suspected areas and if the engine idle increases or decreases, that would probably be the leak). Check loose hose clamps for rubber hoses and check for broken or cracked hose lines too.

From TSB
P0171 - System Too Lean (Bank 1) The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The code is set when the adaptive fuel tables reach a rich calibrated limit.
Fuel System:
�· Contaminated fuel injectors
�· Low fuel pressure or running out of fuel (fuel pump, filter, fuel supply line restrictions)
�· Vapor recovery system (VMV)

Induction System:
�· MAF contamination
�· Air leaks between the MAF and throttle body
�· Vacuum leaks
�· PCV system concern
�· Improperly seated engine oil dipstick

EGR System:
�· Leaking gasket
�· Stuck EGR valve
�· Leaking diaphragm or EVR

Base Engine:
�· Exhaust leaks before or near the HO2S
�· Secondary air concern

Powertrain Control System:
�· PCM concern

My car is a 2000 contour with the 2.5 duratec and an automatic transmission. It also seems to be eating gas like crazy if that might help narrow it down.