What would generally cause this?

Stanglover96 · Nov 21, 2004

P0171 System Too Lean - Bank No. 1.

I have an exhaust leak on the passenger side somewhere, and I've had 3 hrs sleep and I got to thinking. What if it reads lean because the computer is sending extra fuel to compensate for the extra air getting into the cylinder from the leak? Am I way off base or is it something simple? Thanks for reading.

twogts4us · Nov 21, 2004

No, you're not off base - that's likely your problem. Get it fixed and clear the code.

CRZYHRSGT · Nov 21, 2004

Sounds like your exhaust leak is upstream from your oxygen sensor. Seeing that you have an O/R pipe, you should only have 1 sensor on each bank, so you don't have to worry about if its the front or rear sensor on bank 1. Like twogts4us said, fix your leak, clear your code and it should fix your problem.

joshheat25 · Nov 21, 2004

whoa hey I have this same code come up on my car too and I have cats and no exhaust leak here is a website that shows you everything and more than you need to know that it can possibly be I am takiing my car tomorrow to see what it really is!

http://www.v8sho.com/SHO/TSB0197HO2SServiceTips.htm

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

joshheat25 · Nov 21, 2004

Check all of your hoses leading to your plentum and also check above the O2 sensors right after the exhaust manifolds for a leak!

bdcardinal · Nov 21, 2004

check the 02 sensors. it probably isnt a vacuum leak because that would show up as a systemic problem, both banks would be lean.

CRZYHRSGT · Nov 22, 2004

joshheat25 said:
whoa hey I have this same code come up on my car too and I have cats and no exhaust leak here is a website that shows you everything and more than you need to know that it can possibly be I am takiing my car tomorrow to see what it really is!

http://www.v8sho.com/SHO/TSB0197HO2SServiceTips.htm

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

Don't want to start a debate, but OBDII cars can pinpoint the problem a heck of a lot better than pretty much pegging everything under the hood. The link seems almost too informative. By the code pinpointing Bank 1, you can cut out 3/4 of the things listed(things that equally effect the left and right banks). Most of these should have their own codes,also. Plus, with a known exhaust leak on the passanger side (Bank 1), it becomes pretty much a no-brainer.

What would generally cause this?

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