P0171

P0171-FUEL SYSTEM 1/1 LEAN

For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The fuel feedback system will maintain a stoichiometric fuel/air mixture, 14.7:1, by modifying the injector pulsewidth according to the oxygen content of the exhaust gas. The Powertrain Control Module (PCM) makes short term and long term fuel corrections to maintain stoichiometric fuel/air ratio for best catalytic converter efficiency. Short term fuel correction is based on upstream O2 sensor output and is designed for quick engine response. The long term fuel correction compensated for variations in the engine specifications, sensor tolerances and component aging and is designed to correct rich and lean conditions over a longer period of time.

- When Monitored:
With the engine running in closed loop, the ambient/battery temperature above -7° C (20° F) and altitude below 8500 ft.

- Set Condition:
The Powertrain Control Module (PCM) monitors the Adaptive Memory factor (a combination of Short Term Adaptive and Long Term Adaptive). If the total fuel addition exceeds a calibrated threshold for an extended period, a fuel system lean fault is stored. If the total fuel subtraction exceeds a calibrated threshold, a fuel system rich fault is stored. Two Trip Fault. Three good trips to turn off the MIL.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. DTC IS ACTIVE
1. Diagnose and repair any other active component or circuit DTCs before continuing with this procedure.
2. Turn the ignition on.
3. With the scan tool, select View DTCs. Copy DTC and Freeze Frame information.
4. Start the engine and allow it to reach operating temperature.

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.

NOTE: Attempt to operate the vehicle under conditions similar to which the DTC was set.

NOTE: It may be necessary to test drive the vehicle within the DTC monitoring conditions in order for this DTC to set.

5. With a scan tool, select View DTCs.

Is the status Active for this DTC?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test.

2. CHECKING THE EXHAUST SYSTEM FOR LEAKS
1. Perform the diagnostic procedure for CHECKING THE EXHAUST SYSTEM FOR LEAKS. . Checking The Exhaust System For Leaks

Were any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. . Powertrain Verification Test

No

- Go To 3

3. CHECKING THE FUEL DELIVERY SYSTEM
1. Perform the diagnostic procedures for FUEL PRESSURE LEAK DOWN and FUEL DELIVERY SYSTEM OUTPUT - FLOW TEST. . Checking The Fuel Delivery System

Were any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 4

4. CHECKING THE ENGINE COOLANT TEMPERATURE SENSOR OPERATION
1. Perform the diagnostic procedure for CHECKING THE ENGINE COOLANT TEMPERATURE SENSOR OPERATION. . Checking The Engine Coolant Temperature Sensor Operation

Were any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 5

5. CHECKING THE MAP SENSOR OPERATION
1. Perform the diagnostic procedure for CHECKING THE MAP SENSOR OPERATION. . Checking The MAP Sensor Operation

Were any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 6

6. CHECKING THE OXYGEN SENSOR OPERATION
1. Perform the diagnostic procedure for CHECKING THE OXYGEN SENSOR OPERATION. . Checking The Oxygen Sensor Operation

Were any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 7

7. CHECKING THE ENGINE MECHANICAL SYSTEM
1. Perform the diagnostic procedure for CHECKING THE ENGINE MECHANICAL SYSTEM. . Checking The Engine Mechanical System

Were any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 8

8. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors relative to the components tested in this procedure.
- Look for any chafed, pierced, pinched or partially broken wires.
- Look for broken, bent, pushed out or corroded terminals.
- Monitor the scan tool data relative to the components tested in this procedure and wiggle test the wiring and connectors.
- Look for the data to change or for a DTC to set during the wiggle test.
- Perform any Technical Service Bulletins that may apply.

Were any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace and program the Powertrain Control Module (PCM). Powertrain Control Module - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.