P0171 Fuel System Bank 1 Sensor 1 Lean

P0171 Fuel System Bank 1 Sensor 1 Lean - The Powertrain Control Module (PCM) multiplies the short term adaptive value and the long term adaptive value together. If the total corrective value is above a calibrated threshold for than 30 seconds, a fault is set. The MIL light illuminate.

When monitored P0171 code:

• With the engine running.
• Upstream closed loop fuel control.
• Ambient/battery temperature above -6.7°C (20°F).
• Battery voltage above 10.99 volts.
• Attitude below 2590.8 m (8500 ft)

Possible causes P0171 code:

• Restriced fuel supply line.
• Fuel Pump inlet strainer plugged.
• Fuel Pump Module
• O2 signal circuit.
• O2 return circuit.
• O2 sensor.
• MAP sensor.
• ECT sensor.
• Engine mechanical.
• Fuel filter/pressure regulator.
• Powertrain Control Module (PCM).

Diagnose P0171 Fuel System Bank 1 Sensor 1 Lean

Step 1. Check active DTC

Note : Check for contaminats that may have damaged an O2 sensor contaminated fuel, unapproved silicone, oil and coolant.

Start the engine.
Allow the engine to reach normal operating temperature.
With the scan tool, read DTC.

Note : It may be necessary to drive the vehicle to meet the conditions to set this DTC, try to repeat the conditions in which the fault originally set by reviewing the Freeze Frame data.

Is the DTC active or pending?

Yes, go to step 2.

No, perform the PCM intermittent condition.

Step 2. Check the fuel delivery system

Perform the CHECKING THE FUEL DELIVERY SYSTEM test procedure (see Sitemaps or labels this site).

Were any problems found?

Yes, repair as necessary.

No, go to step 3.

Step 3. Exhaust system for leaks

Perform the CHECKING THE EXHAUST SYSTEM FOR LEAKS test procedure this site (see Sitemaps or labels)

Were any problems found?

Yes, repair as necessary.

No, go to step 4.

Step 4.engine coolant temperature sensor operation

Note : For best result, allow the vehicle to sit long enough for the engine to cool down near ambient temperature.

Turn the ignition on.
With the scan tool, read the Engine Coolant Temperature degree 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 ambient temperature.

Note : If engine coolant temperature is above 82°C (180°F), allow the engine to cool until 65°C (150°F) is reached.

Start the engine.
During engine warm up monitor the Engine Coolant Temperature degree value. The temperature value change should be a smooth transition from start up to normal operating 82°C (180°F). Also monitor the actual coolant temperature with a digital thermometer at or near the ECT sensor and thermostat positions.

Note : As the engine warms up to operating temperature, the actual coolant temperature (thermometer reading) and the scan tool Engine Coolant Temperature degree values should stay relatively close to each other.

Was the digital thermometer readings relatively close to the scan reading for the ECT sensor?

Yes, go to step 5

No, replace the Engine Coolant Temperature (ECT) sensor.

(Sorry!!! Step 5-9, refer to code P0174)
Step 5 . Check the Oxygen sensor operation

Step 6. O2 sensor 1/1 Heater operation

Step 7. Check the MAP sensor operation

Step 8. Engine Mechanical
Step 9. Check related PCM and component connections

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