Thread: PO171 Code
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Old 11-30-2009, 05:28 PM   #2
blen_to
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Default Re: PO171 Code

Here you go...I hope it helps a bit>


DTC P0171

* Fuel Trim System Lean


Conditions for Running the DTC

P0171

* DTCs P0030, P0031, P0032, P0068, P0071, P0072, P0073, P0074, P009A, P0101, P0102, P0103, P0111, P0112, P0113, P0114, P0116, P0117, P0118, P0119, P0122, P0123, P0130, P0131, P0132, P0133, P0134, P0135, P0201, P0202, P0203, P0204, P0222, P0223, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0301, P0302, P0303, P0304, P0335, P0336, P0340, P0341, P0365, P0366, P0443, P0458, P0459, P0496, P1101, P2227, P2228, P2229, P2297, P2A00 are not set.
* The engine is in CL status.
* The engine coolant temperature (ECT) is warmer than 65.3C (149.5F).
* The intake air temperature (IAT) is warmer than -9.8C (+14.4F).
* The engine speed is greater than 608 RPM.
* The mass air flow (MAF) is within a calibrated range.
* The barometric pressure (BARO) is more than 70 kPa

Conditions for Setting the DTC

P0171

* The long term FT weighted average value is more or less than a calibrated value.
* The above condition is present for approximately 3 minutes after the conditions for running the DTC have been met.

Circuit/System Testing

Allow the engine to reach operating temperature. With the engine running, observe the Long Term FT parameter with a scan tool. The value should be less than approximately 18 percent with the engine running at operating temperature.

If the value is not less than 18 percent, inspect for the following:

* With the ignition ON and the engine OFF, observe the BARO sensor parameter. The BARO sensor pressure should be within the range specified for your altitude. Refer to Altitude Versus Barometric Pressure (See: Specifications\Altitude Versus Barometric Pressure) .

If the BARO sensor does not indicate the correct barometric pressure, refer to DTC P2227, P2228, or P2229 (See: P2227) .

* With the engine idling, observe the mass air flow (MAF) sensor parameter. The MAF sensor parameter should be between 2-6 g/s at idle.

If the MAF sensor parameter is not between 2-6 g/s at idle, refer to DTC P0101 or P1101 (See: P0101) or DTC P0102 or P0103 (See: P0102) .

* Vacuum hoses for splits, kinks, and improper connections
* Insufficient fuel in the tank
* Low fuel pressure-Refer to Fuel System Diagnosis (See: Component Tests and General Diagnostics) .
* Ethanol concentration greater than 15 percent-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (See: Component Tests and General Diagnostics\Alcohol/Contaminants-in-Fuel Diagnosis) .
* Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (See: Component Tests and General Diagnostics\Alcohol/Contaminants-in-Fuel Diagnosis) .
* Malfunctioning fuel injectors-Refer to Fuel Injector Diagnosis (See: Component Tests and General Diagnostics\Fuel Injector Diagnosis) .
* Missing, loose, or leaking exhaust components from the HO2S forward-Refer to Symptoms - Engine Exhaust (See: Engine, Cooling and Exhaust\Exhaust System\Testing and Inspection\Symptom Related Diagnostic Procedures\Symptoms - Engine Exhaust) .
* Vacuum leaks at the intake manifold, the throttle body, and the injector O-rings
* The air induction system and the air intake ducts for leaks or for a missing air filter element
* A cracked EVAP canister
* Evaporative pipes obstructed or leaking
* The crankcase ventilation system for leaks-Refer to Crankcase Ventilation System Inspection/Diagnosis (See: Emission Control Systems\Positive Crankcase Ventilation\Testing and Inspection) .
* The HO2S for improper installation and for electrical wires or connectors that may have contacted the exhaust system
* The HO2S signal circuit open, shorted to ground, or shorted to the low reference circuit
* Malfunctioning engine components-Refer to Symptoms - Engine Mechanical (See: Engine, Cooling and Exhaust\Engine\Testing and Inspection\Symptom Related Diagnostic Procedures\Symptoms - Engine Mechanical) .

Repair Instructions

* Air Cleaner Assembly Replacement (See: Fuel Delivery and Air Induction\Air Cleaner Housing\Service and Repair)
* Air Cleaner Inlet Duct Replacement (See: Fuel Delivery and Air Induction\Air Cleaner Fresh Air Duct/Hose\Service and Repair)
* Evaporative Emission Canister Replacement (See: Emission Control Systems\Evaporative Emission Control Canister\Service and Repair)
* Evaporative Emission Canister Purge Solenoid Valve Replacement (See: Emission Control Systems\Canister Purge Solenoid\Service and Repair)
* Evaporative Emission Canister Vent Solenoid Valve Replacement (See: Emission Control Systems\Canister Vent Valve\Service and Repair\Evaporative Emission Canister Vent Solenoid Valve Replacement)
* Fuel Feed Intermediate Pipe Replacement (See: Fuel Delivery and Air Induction\Fuel Supply Line\Service and Repair)
* Fuel Pump Fuel Feed Hose Replacement - Front (See: Fuel Delivery and Air Induction\Fuel Pump\Service and Repair\Fuel Pump Fuel Feed Hose Replacement - Front)
* Fuel Pump Fuel Feed Hose Replacement - Rear (See: Fuel Delivery and Air Induction\Fuel Pump\Service and Repair\Fuel Pump Fuel Feed Hose Replacement - Rear)
* Fuel Injector Replacement (See: Fuel Delivery and Air Induction\Fuel Injector\Service and Repair)
* Fuel Tank Fuel Pump Module Replacement (See: Fuel Delivery and Air Induction\Fuel Pump\Service and Repair\Fuel Tank Fuel Pump Module Replacement)
* Heated Oxygen Sensor 1 Replacement (See: Oxygen Sensor\Service and Repair\Heated Oxygen Sensor 1 Replacement)
* Barometric Pressure Sensor Replacement (See: Barometric Pressure Sensor\Service and Repair)
* Mass Airflow Sensor Replacement (See: Air Flow Meter/Sensor\Service and Repair)
* Throttle Body Assembly Replacement (See: Fuel Delivery and Air Induction\Throttle Body\Service and Repair)

Repair Verification

Important: After repairs, use the scan tool Fuel Trim Reset function in order to reset the Long Term Fuel Trim.

1. Install any components or connectors that have been removed or replaced during diagnosis.
2. Perform any adjustment, programming, or setup procedures that are required when a component or module is removed or replaced.
3. Turn ON the ignition, with the engine OFF. Important: DO NOT clear codes with the engine running. The codes may reset in the same ignition cycle.
4. Clear the DTCs.
5. Turn OFF the ignition for 60 seconds.
6. Start the engine.
7. Duplicate the Conditions for Running the DTC and use the Freeze Frame/Failure Records, if applicable, in order to verify the DTC does not reset. If the DTC resets, or another DTC is present, refer to the Diagnostic Trouble Code (DTC) List - Vehicle (See: Diagnostic Trouble Code Descriptions\Diagnostic Trouble Code (DTC) List) and perform the appropriate diagnostic procedure.
8. To verify that the performance of the catalytic converter has not been affected by the condition that set this DTC, perform the Repair Verification for DTC P0420. Refer to DTC P0420 (See: P0420) ..
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