DTC P1171 - Fuel System Lean During Acceleration

Perform On-Board Diagnostic (OBD) System Check. Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. Go to next step.
If any other component-related DTCs are set, diagnose them first. If no other DTC is present, go to next step.
Check fuel level. Add fuel if tank is almost empty. If fuel was added, go to next step. If no additional fuel was required, go to step 5).
Start vehicle and bring engine to normal operating temperature. Raise engine speed to 1200 RPM and using scan tool observe HO2S No. 1 voltage. If scan tool reading toggle between .1 and .9 volt, see INJECTOR BALANCE TEST in SYSTEM/COMPONENT TESTS article. If voltage is not as specified, go to next step.
Turn ignition off. Relieve fuel pressure and install fuel pressure gauge. Start engine, bring to normal operating temperature and allow it to idle. Disconnect vacuum line going to fuel pressure regulator and read pressure gauge. If pressure is 41-47 psi (2.9-3.3 kg/cm² ), see OBD II SYSTEM CHECK in BASIC TESTING article. If pressure reading is not as specified, go to next step.
Check for restricted fuel lines or filter. If problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
Turn ignition on, engine off. Using scan tool, turn on fuel pump. With fuel pressure gauge still connected, pinch off fuel return line, not allowing fuel pressure to exceed 60 psi (4.2 kg/cm² ). Manipulate fuel line to raise pressure greater than 47 psi (3.3 kg/cm² ). If pressure rises greater than 47 psi (3.3 kg/cm² ), check for an intermittent problem. See TESTS W/O CODES article. If pressure does not rise to 47 psi (3.3 kg/cm² ), go to next step.
Check for faulty fuel pump, restricted fuel pump strainer, incorrect fuel pump, incorrect fuel grade or hot fuel. If any problem is found, repair as necessary. Retest system.