Troubleshooting Chevy Colorado P0171

This is part 2 of my video series where I am attempting to troubleshoot a P0171 "Bank 1 system too lean" check engine light on our first generation 2007 Chevy Colorado. This is one of the most challenging codes to diagnose due to the large number of systems and issues that can cause it. In part 1 we did a fuel pressure test and discussed/replaced some parts:    • Chevy Colorado fuel pressure test, P0171 -...   In this next video we discuss inspection and/or replacement of additional components including the exhaust manifold, PCV "dirty" air 90-degree hose, the hose between the throttle body and evap purge valve on the side of the motor, and the oxygen sensors. After this video was recorded all listed parts were replaced. Unfortunately this did not resolve the issue. The check engine light came back on two days later. Parts previously replaced include: Air filter PCV clean air hose between resonator and top of engine New MAP & MAF Cleaned throttle body Changed oil Ran a couple tanks of "premium" gas through the system No detectable vacuum leaks. Sprayed two cans of throttle body cleaner around the throttle body, intake, brake booster, and sides of engine. No perceptible change in RPM's to indicate a vacuum leak Fuel pressure "seems" okay. Holds at 50 psi with key on, engine off. Fluctuates between 56-60 psi with engine idling, steady 58 psi at 1500 rpm After further discussion, we have gone back to the original theory that the replacement fuel pump is defective. Our pressure test showed 58 psi, however from discussion it appears that anything below 62 psi can cause the lean condition. Next step will most likely be to replace the pump again. If anyone has any other ideas, please drop them in the comments! Link to main discussion: https://www.355nation.net/threads/nee... Links to other videos mentioned: MAP & MAF sensors:    • How to replace MAF and MAP sensors in a Ch...   Air filter:    • How to change an air filter in a Chevy Col...   Oxygen sensors:    • How to replace oxygen sensors in Chevy Col...   Purge valve solenoid:    • How to replace Chevy Colorado purge valve ...   Air pump check valve:    • How to replace air/smog pump check valve i...   VVT solenoid:    • How to replace air filter, VVT solenoid, a...