2015 Chevy Silverado P0171 and P0174 Lean Both Banks - Hesitation on Accel

Question

My 5.3 Silverado just started throwing lean codes on both banks and it feels like it's down on power when I pull away from a stop. The idle is a bit rough and I can hear a slight whistling sound coming from the top of the engine when it is cold. I am worried about burning a valve if I keep driving it like this.

turbo_tony · Accepted Answer

The issue was a cracked PCV Foul Air Tube (Part #12673134) located at the rear of the driver side valve cover. The plastic had become brittle and snapped, causing a massive vacuum leak. I replaced the tube for about $25 and also tightened the intake manifold bolts to 89 lb-in as a few were loose. Fuel trims returned to +/- 3% immediately and the codes have stayed off for 500 miles.

Carlos Diaz · Answer

Don't forget to check the EVAP purge solenoid. If it's stuck open, it will draw unmetered air from the gas tank and lean out both banks simultaneously.

Greg Walters · Answer

Check your long-term fuel trims at idle versus 2500 RPM. If the trims improve at higher RPMs, you definitely have a vacuum leak behind the throttle body.

Jake Morrison · Answer

These EcoTec3 engines are known for the PCV tube cracking or the intake manifold bolts backing out slightly. Spray some brake cleaner around the intake gaskets while it's idling to see if the RPMs jump.

2015 Chevy Silverado P0171 and P0174 Lean Both Banks - Hesitation on Accel

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