Originally posted by salmon:
the check engine light just on and off couple times and bothering me so much.the technician told me the error code are:P0171 and P0174.he said it means the computer thought some times there were too much gas got into engine.maybe the sensor is down.they need long time to find what happened.....



Most of the time, this set of codes is caused 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.
P0174 - System Too Lean (Bank 2-Radiator side)
P0171 - System Too Lean (Bank 1-Firewall side)
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

"Always do the cheap and easy ones first." 1996 V6 ATX 96K miles