Fuel Pump Concern
This bulletin applies to 2014-2019 GMC Sierra and 2015-2019 Yukon vehicles. A vehicle may have a concern with an SES lamp on and a rich condition DTC P0172 and P0175.
Disconnect the dirty side of the PCV system. Plug the vacuum supply. Start the engine and monitor the fuel trims in closed loop. If the fuel trims return to normal, this is a good indication that the high pressure fuel pump is leaking. According to GM, “with this concern, we do not see a lot of fuel in the crank case, so changing the oil may not isolate the concern.”
When the high pressure fuel pump leaks, the PCV will pull the fuel mist straight into the intake causing the concern.