Check for a broken hose, leaks at gaskets near the throttle body, EGR valve or exhaust.
From TSB.
Edit. From TSB. Do the cheap and easy ones first.
P0171 - System Too Lean (Bank 1), P0174 - (Bank 2). 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
Last edited by Tony2005; 02/21/06 02:35 PM.