LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Dodge and Ram >> 2003 >> Durango Base, 5.9 Z, 4WD, Part Time >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics - 5.9L >> Diagnostic Tests >> DTC P0171: 1/1 Fuel System Lean Or DTC P0174: 2/2 Fuel System Lean >> Testing
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC P0171: 1/1 Fuel System Lean Or DTC P0174: 2/2 Fuel System Lean: Testing

NOTE: Check for contaminants that may have damaged the O2 sensor, such as contaminated fuel, unapproved silicone, oil or coolant.
  1. Turn ignition on, with engine off. With the DRBIII® scan tool, read the DTCs and record the related freeze frame data. Is the Good Trip Counter displayed and equal to zero? If yes, go to next step. If no, see INTERMITTENT CONDITION  under SELF-DIAGNOSTIC SYSTEM.
    2. WARNING: The fuel system is under a constant pressure, even with the engine off. Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released. See FUEL SYSTEM PRESSURE RELEASE .
  2. Release fuel pressure. See FUEL SYSTEM PRESSURE RELEASE . Install a fuel pressure gauge to fuel pressure test port. Turn ignition on, with engine off. With the DRBIII® scan tool, actuate the Automatic Shutdown (ASD) Fuel System test and observe the fuel pressure gauge. Fuel pressure specification is 44.2-54.2 psi (305-373 kPa). Turn the ignition off. Stop all actuations. Choose a conclusion that best matches fuel pressure reading. 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, replace the fuel filter/pressure regulator.
  3. Release fuel pressure. See FUEL SYSTEM PRESSURE RELEASE . Raise vehicle on hoist, and disconnect the fuel pressure line at the fuel pump module. Connect Fuel Line Adapter (6539 for 5/16" fuel line or 6631 for 3/8" fuel line) between disconnected fuel pressure line and fuel pump module. Attach a fuel pressure test gauge to the "T" fitting of the adapter. Turn ignition on, with engine off. With the DRBIII® scan tool, actuate the ASD Fuel System test and observe the fuel pressure gauge. Turn the ignition off. Stop all actuations. Fuel pressure specification is 44.2-54.2 psi (305-373 kPa). Is the fuel pressure within specification? If yes, repair or replace fuel supply line as necessary. If no, go to next step.
  4. Release fuel pressure. See FUEL SYSTEM PRESSURE RELEASE . Remove the fuel pump module from the fuel tank and inspect the fuel pump inlet strainer. Is the fuel pump inlet strainer plugged? If yes, replace the fuel pump inlet strainer. If no, go to next step.
  5. There are no possible causes remaining, replace the fuel pump module.
  6. Turn the ignition off. Wait a minimum of 10 minutes to allow the O2 sensor and exhaust system to cool down before continuing the test. Turn ignition on, with engine off. With the DRBIII® scan tool, read the O2 sensor voltage. Is the voltage more than 4.5 volts? If yes, go to next step. If no, go to step  13.
  7. Turn the ignition off. Wait a minimum of 10 minutes to allow the O2 sensor to cool down before continuing the test. Turn ignition on, with engine off. With the DRBIII® scan tool, actuate the O2 Heater Test. With the DRBIII® scan tool, monitor the O2 sensor voltage for at least 2 minutes. Does the voltage stay at more than 4.5 volts? If yes, replace the O2 sensor. If no, go to next step.
    8. NOTE: The throttle must be against the stop in this step.
  8. With the DRBIII® scan tool, read TP sensor voltage. Is the voltage 0.92 volt or less with the throttle closed? If yes, go to next step. If no, check for a binding throttle condition. If okay, replace the TP sensor.
  9. With the DRBIII® scan tool, read the TP sensor voltage. While monitoring the DRBIII® scan tool, slowly open and close the throttle. Does the voltage increase and decrease smoothly? If yes, go to next step. If no, replace the TP sensor.
    10. NOTE: If engine will not idle, maintain a constant RPM more than idle.
  10. Turn the ignition off. Connect a vacuum gauge to a manifold vacuum source. Start the engine and allow it to idle. With the DRBIII® scan tool in sensors, read the MAP sensor vacuum value. Is the DRBIII® scan tool reading within 1 in. Hg of the vacuum gauge reading? If yes, go to next step. If no, replace the MAP sensor. Remove the vacuum gauge before continuing.
    11. NOTE: For this test to be valid, thermostat must be operating properly. This test works best if performed on a cold soak engine. If engine coolant temperature is more than 180°F (82°C), allow the engine to cool until 150°F (65°C) is reached.
  11. Turn ignition on, with engine off. With the DRBIII® scan tool in sensors, read the Eng Coolant Tmp Deg value. If the engine was allowed to sit overnight (cold soak), the temperature value should be a sensible value that is somewhere close to the surrounding temperature (ambient temperature). Start the engine. During engine warm-up, monitor the Eng Coolant Tmp Deg value. The value change should be a smooth transition from start-up to normal operating temperature. The value should reach at least 180°F (82°C). Was the Eng Coolant Tmp Deg value increase a smooth transition and did it reach at least 180°F (82°C)? If yes, go to next step. If no, replace the ECT sensor.
  12. Check for any of the following conditions/mechanical problems:
    • Air induction system must be free from leaks.
    • Engine vacuum must be at least 13 in. Hg with transmission in Neutral.
    • Engine valve timing must be within specifications.
    • Engine compression must be within specifications.
    • Exhaust system must be free of any restrictions or leaks.
    • Engine PCV system must flow freely.
    • Torque converter stall speed must be within specifications.
    • Power brake booster must not have any internal vacuum leaks.
    • Fuel must be free of contamination.
    • Check air intake system for restrictions.
    • Ensure proper fuel injector driver wiring is installed on correct fuel injector. Ensure fuel injector is not plugged or restricted.

    Are there any engine mechanical problems? If yes, repair as necessary. If no, see INTERMITTENT CONDITION  under SELF-DIAGNOSTIC SYSTEM.

  13. Turn the ignition off. Wait a minimum of 10 minutes to allow the O2 sensor to cool down before continuing the test. Turn ignition on, with engine off. With the DRBIII® scan tool, read the O2 sensor voltage. Is the voltage more than 4.5 volts? If yes, replace the O2 sensor. If no, go to next step.
  14. Turn the ignition off. Disconnect the PCM harness connectors. Measure the resistance between ground and the O2 sensor signal circuit at the PCM harness connector. Is the resistance less than 100 ohms? If yes, repair the short to ground in the O2 sensor signal circuit. If no, go to next step.
    15. NOTE: Before continuing, disconnect the PCM harness connectors and check the related wiring terminals for corrosion, damage or terminal push out. Repair as necessary.
  15. Using the wiring diagram as a guide, inspect the wire harness and connectors. Visually inspect the related wire harness. Look for any chafed, pierced, pinched, or partially broken wires. Visually inspect both the component and the PCM connectors. Pay particular attention to all power and ground circuits. If there are no possible causes remaining, replace and program the PCM. See PROGRAMMING .
scientia non olet · About LEMON Manuals