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DTC P0171: 1/1 Fuel System Lean

NOTE: Fuel system lean condition is monitored when engine is running in closed loop, ambient temperature is more than 20°F (-7°C), battery temperature is more than 20°F (-7°C) and altitude is less than 8000 feet. DTC may be stored in Powertrain Control Module (PCM) if PCM multiplies short term compensation by long term adaptive and a certain percentage is exceeded for 2 trips. Possible causes are: defective fuel pump module, defective Throttle Position (TP) sensor, restricted fuel inlet strainer on fuel pump, defective Engine Coolant Temperature (ECT) sensor, defective Manifold Absolute Pressure (MAP) sensor, engine mechanical problem, defective fuel filter or defective fuel pressure regulator.
  1. Using scan tool, check for DTCs. If GLOBAL GOOD TRIP counter is not displayed and equal to zero, go to next step. If GLOBAL GOOD TRIP counter is displayed and equal to zero, go to step  3 .
  2. At this time, conditions for fuel system lean condition does not exist or is an intermittent problem. Using scan tool, read FREEZE FRAME data and FUEL SYSTEM SIMILAR CONDITIONS. Attempt to duplicate the conditions when DTC was set. If DTC for fuel system lean condition reoccurs, repeat DTC test procedures. If DTC for fuel system lean condition does not reoccur, perform TEST VER-5A2  .
  3. Turn ignition on with engine off. Using scan tool, read Throttle Position (TP) sensor voltage while slowly opening and closing throttle. If TP sensor voltage changes smoothly while opening and closing throttle, go to next step. If TP sensor voltage does not change smoothly while opening and closing throttle, replace TP sensor. Perform TEST VER-5A2  .
  4. Ensure ignition is on. Using scan tool, read TP sensor voltage with throttle fully closed. If TP sensor voltage is .92 volt or less with throttle closed, go to next step. If TP sensor voltage is more than .92 volt with throttle closed, replace TP sensor. Perform TEST VER-5A2  .
  5. Ensure ignition is on. Using scan tool, read Engine Coolant Temperature (ECT) sensor value to indicate engine coolant temperature. If engine coolant temperature is more than 180°F (82°C), allow engine to cool until engine coolant temperature is 150°F (66°C). Start engine.
  6. Using scan tool, monitor ECT sensor value while warming engine until engine coolant temperature is more than 180°F (82°C). If ECT sensor value increases to at least 180°F (82°C), go to next step. If ECT sensor value does not increase to 180°F (82°C), replace engine coolant temperature sensor. Engine coolant temperature sensor is located near thermostat housing and contains a Black/Light Blue wire and Tan/Black wire in the connector. Perform TEST VER-5A2  .
  7. Using scan tool, read ECT sensor value to indicate engine coolant temperature. If engine coolant temperature is more than 180°F (82°C), allow engine to cool until engine coolant temperature is 150°F (66°C). Start engine if engine is not previously started.
  8. Using scan tool, monitor ECT sensor value while warming engine until engine coolant temperature is more than 180°F (82°C). If ECT sensor value increases in a smooth transition, go to next step. If ECT sensor value does not increase in a smooth transition, replace engine coolant temperature sensor. Engine coolant temperature sensor is located near thermostat housing and contains a Black/Light Blue wire and Tan/Black wire in the connector. Perform TEST VER-5A2  .
  9. Turn ignition off. Connect vacuum gauge to engine vacuum source. Start engine and allow engine to idle. If engine will not idle, maintain a constant RPM above idle. Using scan tool, read MAP sensor vacuum. If MAP sensor vacuum is within one in. Hg of engine vacuum on vacuum gauge, MAP sensor is operating properly. Go to next step. If MAP sensor vacuum is not within one in. Hg of engine vacuum on vacuum gauge, replace MAP sensor. See Figure -Figure . Perform TEST VER-5A2  .
  10. Check fuel pressure and fuel pump volume. See TEST NTC-6: CHECKING FUEL DELIVERY (2.4L, 3.3L & 3.8L)  or TEST NTC-7: CHECKING FUEL DELIVERY (3.0L)  . If fuel pressure and fuel pump volume are within specification, go to next step. If fuel pressure or fuel pump volume is not within specification, repair fuel system as necessary. Perform TEST VER-5A2  .
  11. Check following items for possible causes of a fuel system lean condition:
    • Improper engine vacuum (must be at least 13 In. Hg with transaxle in neutral).
    • Compression is not within specification.
    • Improper engine valve timing.
    • Restricted exhaust system.
    • Restricted PCV.
    • Improper torque converter stall speed.
    • Internal vacuum leak in power brake booster.
    • Contaminated fuel.
    • Restricted fuel injectors or improper fuel injector wiring.
  12. If any of the problems listed exist, repair as necessary. Perform TEST VER-5A2  . If none of the problems listed exist, test is complete.
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