CEL Trouble

[jimbbski]

I have had a Cel light come on and running the code reader I come up with a message of: Bank 1 lean. PO171.

Can I assume that bank 1 is the forward bank?

Would this be the O2 sensor on the pre cat or the down streem one? Are them both the same? I have a O2 sensor that is almost new I can replace the defective one with I just want to know which to replace.

[Tony2005]

Bank 1 is firewall side. P0171 is most probably a vacuum leak in that Bank. Check by spraying with carb cleaner, if the idle changes, you found your leak. Most leaks are at hoses or gaskets.

Per 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

[jimbbski]

Thanks for the reply. I didn't think of a vacuum leak. I'll have to check for that. The idle sometimes varies, that is sometimes it idles at about 1100, sometimes about 900 and sometimes normal, about 600-700. Air leaking into the intake could cause this and the lean condition and not the IAC.