I'm not sure I understand your question, because the Diagnostic Trouble Code
(DTC) is pretty self-explanatory.
DTC P0171: System too lean (Bank 1)
It says the system is too lean on bank 1...
A V configured engine has two banks of cylinders (left and right). This
problem is on "Bank 1".
"Too lean" means the O2 sensor on (bank 1, in this instance) is sending a
high voltage signal (consistently higher than .450v) to the PCM, indicating
a lean AFR condition. Lean means, too much air or not enough fuel.
The Oxygen (O2) sensor measures *oxygen* in the exhaust system as a
indication of Air/Fuel (A/F) mixture or Air Fuel Ratio (AFR).
High O2 content = Lean condition (too much air)
Low O2 content = Rich condition (not enough air)
BTW, a high O2 content in the exhaust doesn't necessarily mean there is a
true lean condition. A engine misfire will also cause a high O2 condition
because the oxygen in the offending (misfiring) cylinder isn't being burned
like it would be if there were no misfire. That in turn will cause a false
reading for the PCM. The PCM can't tell if the high O2 content is caused
from a engine misfire or a (true) lean condition (plugged injector, vacuum
leak, etc.). The same thing applies with a exhaust leak. If a exhaust
manifold flange gasket is leaking, it will allow fresh air into the exhaust
system, the O2 sensor sees excess O2 and tells the PCM that there is a lean
condition on that bank.
So don't just assume it's lean. It may very well be but you still don't just
jump to the conclusion that it is. The first step in diagnosing electronic
engine controls is checking the *basics* before jumping into the
Been a long time,
Could also be a bad sensor.
I read something a while back about the O2 sensor. Someone correct me if
I'm wrong. I read that it basically measures heat. Too lean means the
exhaust will be hot, too rich it will be cool. A perfect mixture makes the
sensor happy. I tend to agree with this as I find it hard to believe that a
small device stuck in the exhaust pipe can accurately measure oxygen
Sorry, but your explanation is inaccurate. The oxygen sensor uses an
element that generates a voltage when it senses oxygen. The only thing heat
has to do with it is that the sensors need to be heated above 600*F to
function properly. The O2 sensor will flucutate from lean to rich,
temperature will never fluctuate as quickly as an O2 sensor registers
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.