P2272

P2272 is the Bank 2 downstream O2 stuck-lean fault, only present on V-bank diesels with dual post-cat sensors. Cheapest-first ladder: confirm both banks first - if Bank 1 is healthy and only Bank 2 sensor 2 is pinned lean, inspect the Bank 2 exhaust path from manifold to mid-pipe with a smoke machine at 0.5 psi, since even a hairline crack in the Y-pipe or a leaking up-pipe gasket will pull ambient air across the sensor tip. Caveat: a sticking Bank 2 EGR valve will lean out the right bank only and set P2272 without any sensor fault - always pull EGR position versus commanded data before replacing the sensor.

Vehicle-specific patterns: 2008 to 2010 Ford 6.4L Powerstroke set P2272 from cracked Bank 2 up-pipe at the flange near the turbo pedestal; 2011 to 2016 Duramax LML throw the code from a leaking Bank 2 EGR cooler diluting exhaust; 2011 to 2019 Ford 6.7L Powerstroke set P2272 when the Bank 2 sensor heater fails after a regen cycle; 2007 to 2014 Mercedes ML320/350 BlueTEC OM642 set the code from a cracked Bank 2 manifold. Estimated repair: $120 to $1,800.