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Home >> Chrysler >> 2001 >> PT Cruiser Base, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0171: 1/1 Fuel System Lean >> Testing
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DTC P0171: 1/1 Fuel System Lean: Testing

  1. Turn ignition on. Using scan tool, read DTCs. If GOOD TRIP is displayed and equal to zero, go to next step. If GOOD TRIP is not displayed and equal to zero, go to step  16 .
    WARNING: Fuel system is under constant pressure even when ignition is off. Open fuel system with caution.
  2. Release fuel pressure. See FUEL SYSTEM PRESSURE RELEASE  . Connect fuel pressure gauge to fuel rail. Turn ignition on. Using scan tool, actuate ASD FUEL SYSTEM TEST and observe fuel pressure gauge. Fuel pressure should be 53-63 psi (365-434 kPa). Turn ignition off. If fuel pressure is within specification, go to step  6 . If fuel pressure is less than specification, go to next step. If fuel pressure is more than specification, check fuel return line for restrictions. Repair as necessary. If fuel return line is okay, replace fuel filter/pressure regulator.
  3. Release fuel pressure. See FUEL SYSTEM PRESSURE RELEASE  . Raise vehicle on hoist. Disconnect fuel pressure line from fuel pump module. Connect 5/16 Fuel Line Adapter (6539) between disconnected fuel line and fuel pump module. Connect fuel pressure gauge to "T" on fuel line adapter. Turn ignition on. Using scan tool, actuate ASD FUEL SYSTEM TEST. Observe fuel pressure gauge. Note fuel pressure reading, stop ASD FUEL SYSTEM TEST and turn ignition off. If fuel pressure is 53-63 psi (365-434 kPa), repair or replace fuel supply line as necessary. If fuel pressure is not 53-63 psi (365-434 kPa), go to next step.
  4. Remove fuel pump module from fuel tank. Inspect fuel inlet strainer. If fuel inlet strainer is plugged, replace fuel inlet strainer. If fuel inlet strainer is not plugged, go to next step.
  5. If no other possible causes are remaining, replace fuel pump module.
  6. Start engine and warm to normal operating temperature. Using scan tool, read 1/1 HO2S voltage. Increase engine speed, then let engine idle. If voltage varies from less than .35 volt to more than .53 volt, go to next step. If voltage does not vary from less than .35 volt to more than .53 volt, go to step  13 .
  7. Turn ignition off then on. Using scan tool, monitor TP sensor voltage. Slowly open and close throttle. If voltage change is smooth, go to next step. If voltage change is not smooth, replace TP sensor.
  8. Using scan tool, read TP sensor voltage. Ensure throttle is against throttle stop. If voltage is .92 volt or less with throttle closed, go to next step. If voltage is more than .92 volt with throttle closed, check for binding throttle. Repair as necessary. If throttle is not binding, replace TP sensor.
    NOTE: For the following test to be valid, thermostat must be operating correctly. This test works best if engine was allowed to cool overnight.
  9. Turn ignition off then on. Using scan tool, read ECT sensor value. If engine was allowed to cool overnight, ECT sensor value should be close to ambient temperature. If engine coolant temperature is more than 180°F (82°C), allow engine to cool until 150°F (66°C) is reached. Start engine. During engine warm-up, ECT sensor value should increase smoothly to at least 180°F (82°C). If operation is as specified, go to next step. If operation is not as specified, replace ECT sensor.
  10. Turn ignition off. Visually inspect related wiring harness. Check for chafed, pierced, pinched or partially broken wires. Visually inspect related wiring harness connectors. Check for broken, bent, pushed out or corroded terminals. Refer to any Technical Service Bulletins (TSBs) that may apply. Perform a wiggle test on related wiring harnesses with engine running. Watch for GOOD TRIP counter to change to zero. If a problem is found, repair as necessary. If no problems are found, go to next step.
  11. Connect a vacuum gauge to a manifold vacuum source. Start engine and let it idle. If engine will not idle, maintain a constant RPM above idle. Using scan tool, monitor MAP sensor vacuum value. If scan tool reading is within one in. Hg of vacuum gauge reading, go to next step. If scan tool reading is not within one in. Hg of vacuum gauge reading, replace MAP sensor.
  12. Check for any of the following conditions:
    • Ensure engine vacuum is at least 13 in. Hg at idle in Park or Neutral.
    • Ensure valve timing is correct.
    • Ensure engine compression is within specification.
    • Ensure exhaust system is free from restrictions or leaks.
    • Ensure PCV system flows freely.
    • Ensure torque converter stall speed is within specification.
    • Ensure power brake booster has no internal vacuum leaks.
    • Ensure fuel is not contaminated.
    • Ensure fuel injectors are not restricted.
    • Ensure fuel injector harness connectors are connected to correct fuel injectors.

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

  13. With engine idling, measure voltage drop (backprobe connectors with voltmeter) of signal circuit (Black/Dark Green wire) between 1/1 HO2S harness connector and terminal No. 30 at PCM C1 harness connector. See Figure and Figure . If voltage drop is less than .1 volt, go to next step. If voltage drop is .1 volt or more, repair high resistance in signal circuit.
  14. With engine idling, measure voltage drop (backprobe connectors with voltmeter) of sensor ground circuit (Black/Orange wire) between 1/1 HO2S harness connector and terminal No. 27 at PCM C1 harness connector. If voltage drop is less than .1 volt, go to next step. If voltage drop is .1 volt or more, repair high resistance in sensor ground circuit.
  15. Replace 1/1 HO2S. Operate vehicle under conditions noted in freeze frame. It may be necessary to operate vehicle for more than 2 drive cycles. Using scan tool, monitor 1/1 HO2S voltage and ensure good voltage activity. If DTC does not reset, test is complete. If DTC resets, replace PCM.
  16. Conditions that set DTC are not present at this time. Using scan tool, read freeze frame data and FUEL SYSTEM SIMILAR CONDITIONS WINDOW data. Using this information, try to duplicate operating conditions when DTC was set. Pay particular attention to ECT sensor value and engine RPM. Refer to any Technical Service Bulletins (TSBs) that may apply. If a problem is found, repair as necessary. If no problems are found, test is complete.
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