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Home >> Dodge and Ram >> 2001 >> Durango 5.9 Z, 4WD, Part Time >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0171: 1/1 Fuel System Lean Or DTC P0174: 2/1 Fuel System Lean >> Testing
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DTC P0171: 1/1 Fuel System Lean Or DTC P0174: 2/1 Fuel System Lean: Testing

    NOTE: Check for contaminates which may have damaged HO2S; contaminated fuel, unapproved silicone, oil and/or engine coolant.
  1. Turn ignition on, engine off. Using scan tool, read DTCs. If GOOD TRIP counter for DTC P0171 or P0174 is displayed and displayed count is "0", go to next step. If GOOD TRIP counter for DTC P0171 or P0174 is not displayed or displayed count is not "0", go to step  16.
  2. Turn ignition off. Release fuel pressure. See FUEL SYSTEM PRESSURE RELEASE . Remove test port cap from fuel rail. Install a 0-60 psi (0-4.2 kg/cm2 ) fuel pressure gauge to test port on fuel rail. Turn ignition on, engine off. Using scan tool, actuate ASD fuel system test. Allow fuel pressure gauge to stabilize. Stop ASD fuel system activation. Fuel pressure should be 44.2-54.2 psi (3.23-3.96 kg/cm2 ). If fuel pressure is less than specification, go to next step. If fuel pressure is within specification, go to step  6. If fuel pressure is more than specification, test is complete.
    3. WARNING: High fuel pressure may be present in fuel lines. Open fuel system with caution. See FUEL SYSTEM PRESSURE RELEASE .
    Fig 1: Locating Fuel Filter/Pressure Regulator
    G00010247Courtesy of DAIMLERCHRYSLER CORPORATION
  3. Turn ignition off. Raise and support vehicle. Disconnect fuel pressure line from fuel pump module. See Fig 1. Connect Fuel Line Pressure Test Adapter Hose (6539) or (6631) between disconnected fuel line and fuel pump module. Connect fuel pressure gauge to fuel line adapter hose. Turn ignition on, with engine off. Using scan tool, actuate ASD fuel system test and note fuel pressure. Fuel pressure should be 44.2-54.2 psi (3.23-3.96 kg/cm2 ). If fuel pressure is within specification, stop ASD fuel system activation, release fuel pressure and repair or replace fuel supply line as necessary. If fuel pressure is not within specification, stop ASD fuel system activation and go to next step.
  4. Turn ignition off. Release fuel pressure. See FUEL SYSTEM PRESSURE RELEASE . Remove fuel pump module and inspect fuel inlet strainer. See FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. If fuel inlet strainer is plugged, replace fuel pump inlet strainer. If fuel inlet strainer is not plugged, go to next step.
  5. At this time, fuel pump module is assumed to be defective. Replace fuel pump module.
  6. Turn ignition on, engine off. Using scan tool, read appropriate HO2S voltage. If voltage is 0.4-0.6 volt, go to next step. If voltage is not 0.4-0.6 volt, go to step  13.
  7. Turn ignition off. Wait at least 10 minutes to allow HO2S to cool down (voltage should stabilize to 0.4-0.6 volt). Using scan tool, actuate HO2S HEATER TEST and monitor appropriate HO2S voltage for 2 minutes. If voltage does not stay at 0.4-0.6 volt, go to next step. If voltage stays at 0.4-0.6 volt, replace faulty HO2S.
  8. Ensure ignition is on. Ensure throttle plate is fully closed against stop. Using scan tool, read TP sensor voltage. If voltage is 0.92 volt or less, go to next step. If voltage is more than 0.92 volt, check throttle plate and linkage for binding. Repair throttle plate and linkage as necessary. If throttle plate and linkage are okay, replace TP sensor.
    9. NOTE: Throttle linkage must be moved very slowly while looking for a smooth change in voltage in this step.
  9. Ensure ignition is on. Using scan tool, read TP sensor voltage. Slowly open and close throttle plate while monitoring TP sensor voltage. If voltage increases and decreases smoothly, go to next step. If voltage does not increase and decrease smoothly, replace TP sensor.
  10. Turn ignition off. Connect a vacuum gauge to manifold vacuum source. Start engine and allow it to idle. If engine will not idle, maintain a constant RPM above idle. Using scan tool in SENSOR mode, monitor Manifold Absolute Pressure (MAP) vacuum value. Compare scan tool MAP sensor value with vacuum gauge reading. If scan tool value is within one in. Hg of vacuum gauge, turn ignition off and go to next step. If scan tool value is not within one in. Hg of vacuum gauge reading, replace MAP sensor.
    11. NOTE: For the following diagnostics to be accurate, engine thermostat must be functioning properly. The following procedure works best when engine is allowed to cold soak overnight.
  11. Turn ignition on, engine off. Using scan tool, read ECT sensor value. If ECT reading is more than 180°F (82°C), allow engine coolant temperature to cool down to 150°F (66°C) before proceeding. If engine coolant temperature is 150°F (66°C) or less, start engine and monitor scan tool ECT sensor reading. ECT sensor value should increase smoothly and reach at least 180°F (82°C). If ECT sensor value increases smoothly and reaches at least 180°F (82°C), go to next step. If ECT sensor value does not increase smoothly or does not reach at least 180°F (82°C), check for cooling system concerns. Repair cooling system as necessary. If cooling system is okay, replace ECT sensor.
  12. Check the following additional items as possible mechanical problems:
    • Air induction system must be free of leaks.
    • Engine vacuum must be at least 13 in. Hg with shift selector in Neutral.
    • Engine valve timing must be within specification.
    • Engine compression must be within specification.
    • Engine exhaust system must be free of restrictions or leaks.
    • Engine Positive Crankcase Ventilation (PCV) system must flow freely.
    • Torque converter stall speed must be within specification.
    • Power brake booster must have no internal leaks.
    • Fuel must be free of contamination.
    • Fuel injectors must be free of restrictions.
    • Fuel injector control wires must be installed on correct injector.

    Repair any mechanical problems as necessary. If no mechanical problems exist, test is complete.

  13. Turn ignition off. Disconnect appropriate HO2S connector. Turn ignition on, engine off. Using scan tool, monitor appropriate HO2S voltage. If voltage is not 0.4-0.6 volt, go to next step. If voltage is 0.4-0.6 volt, replace faulty HO2S.
  14. Turn ignition off. Disconnect PCM connectors. PCM is located in engine compartment on passenger-side inner fender panel. Measure resistance of oxygen sensor signal circuit between ground and HO2S harness connector terminal No. 3 (5.9L California) or No. 4 (4.7L and 5.9L except California). See Figure. If resistance is more than 5 ohms, go to next step. If resistance is 5 ohms or less, repair short to ground in HO2S signal circuit between PCM and appropriate HO2S. See WIRING DIAGRAMS article.
  15. At this time, PCM is assumed to be defective. Replace PCM.
  16. At this time, conditions for DTC to set do not exist or fault is an intermittent problem. Start engine and allow it to idle. Ensure engine is at normal operating temperature. Using scan tool, monitor parameters related to DTC while wiggling connectors and wiring harness. If value changes while wiggling connectors and wiring harness, repair connectors and wiring harness where wiggling caused value to change. If value does not change, review FREEZE FRAME DATA using scan tool. Attempt to duplicate condition that caused DTC to set. Check for any related Technical Service Bulletins (TSBs) that may apply. Visually inspect related connectors and wiring harness. Repair connectors and wiring harness as necessary. See WIRING DIAGRAMS article. If no problems are indicated, test is complete.
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