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Home >> Ford >> 2000 >> Contour SE, 2.5 L, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 753 (Engine Controls - Powertrain DTC Charts & Descriptions - CNG, Flex-Fuel & Gasoline) >> Diagnostic Trouble Code (DTC) Charts >> P0171: System Too Lean (Bank 1)

P0171: System Too Lean (Bank 1)

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P0171 - SYSTEM TOO LEAN (BANK 1)

Description:  The adaptive fuel strategy continuously monitors the fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit. Refer to FUEL TRIM for more information.
Possible Causes:  Fuel System
  • Fuel pressure regulator (leaking, faulty).
  • Fuel filter plugged, dirty.
  • Fuel pump (weak, check valve leaking).
  • Leaking/contaminated fuel injectors.
  • Low fuel pressure or running out of fuel.
  • EVAP canister purge valve leaking (when the canister is clean).
  • Fuel supply line restricted.
  • Fuel rail pressure sensor (incorrect reading).

    Air Induction System.

  • Air leaks after the MAF.
  • Vacuum Leaks.
  • PCV system (leak or valve stuck open).
  • Improperly seated engine oil dipstick.

    Exhaust System.

  • Exhaust leaks before or near the HO2Ss (exhaust manifold gasket, mating gaskets).

    EGR system.

  • Vacuum hose disconnected on EGR System Module (ESM) applications.
  • EGR valve tube/gasket leak.
  • EVR solenoid vacuum leak.

    Secondary Air Injection.

  • Damaged/malfunctioning secondary air injection system (mechanically stuck valve).

    Air Measurement System.

  • MAF sensor (contaminated, damaged, or faulty).
Diagnostic Aids:  View Freeze Frame Data to determine the operating conditions when the DTC was set. Observe the LONGFT1 and LONGFT2 PID(s). Refer to ADAPTIVE FUEL DTCS DIAGNOSTIC TECHNIQUES for more information.
Application  Key On Engine Off  Key On Engine Running  Continuous Memory 
Dedicated NGV GO to PINPOINT TEST HA: NATURAL GAS FUEL CONTROL Step 10. GO to PINPOINT TEST HA: NATURAL GAS FUEL CONTROL Step 10. GO to PINPOINT TEST HA: NATURAL GAS FUEL CONTROL Step 10.
All others - - GO to PINPOINT TEST H: FUEL CONTROL Step 17.
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