2015 Tahoe P0171 and P0174 Lean Both Banks - Hesitation on Acceleration

Question

My dash just lit up with a traction control light and check engine light while idling at a red light. The truck feels like it wants to stumble when I tip into the throttle from a stop, but it seems to smooth out once I get up to highway speeds. I hooked up my scanner and I'm seeing positive long-term fuel trims around 22% on both banks.

fleet_chief_42 · Accepted Answer

The issue turned out to be a dry-rotted vacuum line on the EVAP purge solenoid and a leaking intake manifold gasket. I replaced the intake gaskets (ACDelco 12626354) and the purge valve assembly. After torquing the manifold bolts to 89 lb-in in the proper sequence, the long-term fuel trims dropped back down to 3%. Total repair cost was about $85 for parts and 3 hours of my time.

hd_trucker_77 · Answer

Try spraying some brake cleaner or unlit propane around the PCV hose connections and the intake manifold mating surfaces. If the engine RPM jumps, you've found your air leak location.

Kevin Tran · Answer

Check your fuel pressure at the rail. These EcoTec3 engines use a high-pressure direct injection system, but if the low-pressure fuel pump in the tank is failing, it can cause lean codes across the board.

Sarah Thompson · Answer

Since it is affecting both banks equally, you should look for a vacuum leak after the MAF sensor. Check the intake bellows for cracks and listen for a whistling sound around the intake manifold gaskets while the engine is running.

2015 Tahoe P0171 and P0174 Lean Both Banks - Hesitation on Acceleration

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