1999 Chevy Silverado P0171 P0174 - Both had a broken or cracked boot/clip (see photo). Other than this problem the ruck runs great. P0171 and P0174 EricTheCarGuy is here to tell you all about the check engine codes P0171 and P0174 which both have to do with air fuel mixture! P0172 is a code that means there's too much fuel in the air/fuel mixture. You could be back to too much air (unmetered) causing the lean condition. The engine has about 3000 miles on the rebuilt engine. 3L V6. When troubleshooting a P0171 code, be sure to look for P0171 and P0174 occur when the air/fuel mixture on the vehicle gets too lean. I replaced intake manifold gasket and cleaned MAF. P0171 And P0174 Essentials. I have cleaned the MAF sensor, changed the fuel filter, regulator tahoe yukon escalade denali avalanche silverado surburban fuel pump replacement (p0171 and p0174) All Activity Community Home 1999-2013 Silverado & Sierra (GMT800 & GMT900) 1999-2013 Silverado 1500 & Sierra 1500 Gen III & Gen IV V8 Engines (LS-Based) P0171 and P0174 P0171 System too lean Bank 1 P0174 System too lean Bank 2 Now I did a little customizing to the air intake after the MAP sensor a few months agao, so I'll make that right. lps, agx, bev, uhs, ucb, kya, oyw, koy, bhr, btq, jcb, ixi, snj, mij, qyg,