System Too Lean (Bank 2)

Yes, for a few weeks, but a lean mixture runs hot and can eventually damage pistons and the catalytic converter, so do not park the problem indefinitely.

This is the same lean condition as P0171, but on bank 2, the cylinder bank that does not contain cylinder 1, so you only see it on V6, V8, and other two-bank engines. The oxygen sensor on that side keeps reporting too much air for the fuel delivered, and the computer has maxed out its correction. The most telling clue is whether P0171 is stored alongside it: both banks lean at once points at something shared, like a vacuum leak or a dirty airflow sensor, while one bank alone points at that side specifically.

The most likely causes, roughly in order, are a vacuum leak: a cracked intake boot, brittle PCV hose, or leaking intake manifold gasket, which on many V engines fails on one bank first (the leading cause); a dirty or contaminated mass airflow (MAF) sensor under-reporting incoming air (usually sets both P0171 and P0174 together); a leaking or stuck-open purge valve pulling extra air through the evap system; weak fuel pressure from a tired fuel pump or clogged filter. Ask for a smoke test first, since it finds vacuum leaks in minutes, and have the MAF cleaned at the same visit. Pay attention to whether one bank or both are lean, because that single fact steers the whole diagnosis: both banks means look at shared parts like the MAF and fuel pressure, one bank means hunt that side's manifold gasket and hoses. Replacing oxygen sensors on a hunch is the classic wasted spend here, because the sensor is usually telling the truth.

Fixing the underlying problem behind a P0174 code typically runs $130 to $910 at an independent shop, including parts and labor. The exact figure depends on your vehicle and which part turns out to be at fault.