← Back to list

2007 Ford Mustang V6 P0171 and P0175 Codes: Diagnosis and Fix Guide

Model: Ford Mustang v6 2007 Fault Code: P0171 Posted: 2009-05-07 14:51

Hi everyone, I own a 2007 Ford Mustang with a 5.0L V6 engine. Last week, the service light came on, and I started noticing a significant loss of power and hesitation during acceleration—especially when pressing the gas pedal. The RPMs would fluctuate unpredictably. This issue doesn't occur consistently; it's more noticeable after driving for several miles. When I first start the car, everything runs smoothly, but as the engine warms up, the symptoms appear. I used an OBD2 scanner and found two diagnostic trouble codes: P0171 (System Too Lean Bank 1) and P0174 (System Too Lean Bank 2). Some people have suggested it might be related to the gas pump or fuel quality, but I'm not sure if that's accurate. Can anyone confirm what these codes mean and how to fix them? Thanks in advance for any insights!

Related fault codes
P0171P0174
Comments (3)
Anonymous 2009-05-07 16:45

Yes, you can find a detailed solution here—P0171 and P0174 are among the most frequently reported codes on Ford Mustang forums. Before posting a new thread, please review existing discussions. The answers to your question are likely already available in previous posts.

Anonymous 2009-05-07 18:37

Your vehicle enters open-loop fuel control at startup and transitions to closed-loop operation once the engine reaches approximately 180°F. In closed loop, the Engine Control Unit (ECU) monitors air-fuel ratios using sensors like the Mass Airflow (MAF) sensor. If the actual air-to-fuel ratio deviates from the ideal stoichiometric ratio of 14.7:1, or if the ECU cannot maintain stable fuel control, it triggers a lean condition and sets codes P0171 and P0174. The root cause is typically one of several possibilities: an air leak in the intake system, vacuum lines, or a restriction in the fuel delivery system. Since all sensors appear to be functioning correctly, focus should shift to identifying leaks or obstructions. On V6 Ford Mustangs like yours, a common issue is an intake manifold leak—especially if idle behavior is uneven. A can of carburetor or intake cleaner may help detect such leaks; once the idle stabilizes, you’ll know it’s resolved. Recommended steps: 1. Replace the fuel filter and have fuel pressure checked before proceeding further. 2. Inspect key components: - MAF sensor (contaminated, damaged, or malfunctioning) - Fuel pressure regulator (leaking or faulty) - Clogged or dirty fuel filter - Weak fuel pump (check valve leak) - Leaking or contaminated injectors - Low fuel pressure or running out of fuel - EVAP canister purge valve leak (especially when the canister is clean) - Restricted fuel supply lines - Faulty fuel rail pressure sensor 3. Check intake and air induction system: - Air leaks after the MAF sensor - Vacuum leaks - PCV system issues (valve stuck open or leaking) - Improperly seated engine oil dipstick 4. Exhaust system: - Leaks before or near the oxygen sensors (e.g., exhaust manifold gaskets, mating seals) 5. EGR system: - EGR valve tube or gasket leaks - EVR solenoid vacuum leak 6. Secondary air injection system: - Stuck or malfunctioning mechanical valves Once you identify and fix the root cause, clear the codes using an OBD2 scanner and test drive to confirm improvement. Best of luck—Aeroman.

Anonymous 2009-06-24 11:00

What was the final outcome? Did you resolve the issue or are you still experiencing problems?