2008 f150 4.2lt
 

hello all, how can i determine which is bank 1 and bank2 also, which o2 sensor is considered S1 verse S2 Im getting a code p0171 system too lean (Bank 1) I look forward to hearing from anyone thanks

Bank 1 is the one with the #1 cylinder, I'm brainfarting right now, but I think that is the passenger side. There are 4 O2 sensors S1-1 ( also called B1S1) is for Bank 1 at the exhaust manifold. S1-2 is the same side at the cat. S2-1 is the other side at the exhaust manifold and S2-2 is at the cat.

The 171 code usually isn't the o2 sensor (unless you listen to the parts monkies at Auto Zone, so save your money on that one. Most common cause is a vac leak. Check the hose that comes off of the PCV valve, it is probably soft or rotten. That is where the issue is 10 out of 9 times. (haha)

If you use code word 171 in the search and limit the search to the V-6 forum you will get lots of reading and most likely what you need.

good luck

thank-you