Dtc P0171 System Too Lean (Bank 1)

DESCRIPTION

MONITOR DESCRIPTION

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

CONFIRMATION DRIVING PATTERN

WIRING DIAGRAM

INSPECTION PROCEDURE

CHECK FOR ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0171 OR P0172)

CHECK PCV HOSE CONNECTIONS

CHECK AIR INDUCTION SYSTEM

PERFORM ACTIVE TEST USING INTELLIGENT TESTER (CONTROL THE INJECTION VOLUME FOR A/F SENSOR)

READ VALUE USING INTELLIGENT TESTER (COOLANT TEMP)

READ VALUE USING INTELLIGENT TESTER (MAF)

CHECK FUEL PRESSURE

CHECK FOR EXHAUST GAS LEAK

CHECK FOR SPARKS AND IGNITION

INSPECT FUEL INJECTOR ASSEMBLY (INJECTION AND VOLUME)

INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

CHECK TERMINAL VOLTAGE (+B OF AIR FUEL RATIO SENSOR)

CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ECM)

REPLACE AIR FUEL RATIO SENSOR

PERFORM CONFIRMATION DRIVING PATTERN

CHECK HARNESS AND CONNECTOR

CHECK WHETHER DTC OUTPUT RECURS

CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER - ECM)

REPLACE MASS AIR FLOW METER

CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED

CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - A/F RELAY)

INSPECT A/F RELAY

DESCRIPTION

HINT:

1. When DTC P0171 is stored, the actual air-fuel ratio is on the lean side. When DTC P0172 is stored, the actual air-fuel ratio is on the rich side.
   
2. If the vehicle runs out of fuel, the air-fuel ratio is lean and DTC P0171 may be stored. The MIL is then illuminated.
   
3. When the total of the short-term and long-term fuel trim values is within the malfunction threshold (and the engine coolant temperature is higher than 75°C [167°F]), the system is functioning normally.
   

MONITOR DESCRIPTION

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

CONFIRMATION DRIVING PATTERN

1. Connect the intelligent tester to the DLC3.
   
2. Turn the ignition switch to ON and turn the intelligent tester on.
   
3. Clear the DTCs (even if no DTCs are stored, perform the clear DTC operation).
   
4. Turn the ignition switch off and wait for at least 30 seconds.
   
5. Turn the ignition switch to ON and turn the intelligent tester on [A].
   
6. Start the engine and warm it up until the engine coolant temperature is 75°C (167°F) or higher with all the accessories switched off [B].
   
7. With the engine warmed up, idle the engine for 2 minutes or more [C].
   
8. Drive the vehicle at a speed between 60 and 100 km/h (38 and 63 mph) for 5 minutes or more [D].
   

   CAUTION:

   When performing the confirmation driving pattern, obey all speed limits and traffic laws.

9. Enter the following menus: Powertrain / Engine and ECT / DTC [E].
   
10. Read the pending DTCs.
    

    HINT:

    If a pending DTC is output, the system is malfunctioning.

WIRING DIAGRAM

INSPECTION PROCEDURE

HINT:

1. Read freeze frame data using the intelligent tester. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.
   
2. A low air fuel ratio sensor voltage could be caused by a rich air-fuel mixture. Check for conditions that would cause the engine to run rich.
   
3. A high air fuel ratio sensor voltage could be caused by a lean air-fuel mixture. Check for conditions that would cause the engine to run lean.
   
4. Sensor 1 refers to the sensor closest to the engine assembly.
   
5. Sensor 2 refers to the sensor farthest away from the engine assembly.
   

1. Connect the intelligent tester to the DLC3.
   

2. Turn the ignition switch to ON.
   

3. Turn the intelligent tester on.
   

4. Enter the following menus: Powertrain / Engine and ECT / DTC.
   

5. Read the DTCs.
   

   Result

   Result	Proceed to
   P0171 or P0172 is output	A
   P0171 or P0172 and other DTCs are output	B

   HINT:

   If any DTCs other than P0171 or P0172 are output, troubleshoot those DTCs first.

1. Check the PCV hose connections (HILUX_TGN26 RM000001I6600NX_01_0001.html).
   

   OK:

   PCV hose is connected correctly and is not damaged.
   

1. Check the air induction system for vacuum leaks (HILUX_TGN26 RM000001A3W024X_01_0008.html).
   

   OK:

   No leaks in air induction system.
   

1. Connect the intelligent tester to the DLC3.
   

2. Start the engine.
   

3. Turn the intelligent tester on.
   

4. Warm up the engine and run the engine at an engine speed of 2500 rpm for approximately 90 seconds.
   

5. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.
   

6. Perform the Control the Injection Volume for A/F Sensor operation with the engine idling.
   

7. Monitor the output voltages of the air fuel ratio and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2) displayed on the intelligent tester.
   

   HINT:

   1. Change the fuel injection volume within the range of -12.5% to +12.5%. The injection volume can be changed in fine gradations.
      
   2. The air fuel ratio sensor has an output delay of a few seconds and the heated oxygen sensor has a maximum output delay of approximately 20 seconds.
      
   
   

   Intelligent Tester Display (Sensor)	Injection Volume	Status	Voltage
   AFS Voltage B1S1 (Air fuel ratio)	+12.5%	Rich	Below 3.1 V
   AFS Voltage B1S1 (Air fuel ratio)	-12.5%	Lean	Higher than 3.4 V
   O2S B1S2 (Heated oxygen)	+12.5%	Rich	Higher than 0.55 V
   O2S B1S2 (Heated oxygen)	-12.5%	Lean	Below 0.4 V

   
   

   Result

   Status of AFS Voltage B1S1	Status of O2S B1S2	Air Fuel Ratio Condition and Air Fuel Ratio Sensor Condition	Misfire	Suspected Trouble Area	Proceed to
   Lean/Rich	Lean/Rich	Normal	-	-	A
   Lean	Lean	Actual air fuel ratio lean	May occur	PCV valve and hose PCV hose connections Fuel injector blockage Gas leaks from exhaust system Intake system Fuel pressure Mass air flow meter Engine coolant temperature sensor	A
   Rich	Rich	Actual air fuel ratio rich	-	Fuel injector leakage or blockage Gas leaks from exhaust system Ignition system Fuel pressure Mass air flow meter Engine coolant temperature sensor	A
   Lean	Lean/Rich	Air fuel ratio sensor malfunction	-	Air fuel ratio sensor	B
   Rich	Lean/Rich	Air fuel ratio sensor malfunction	-	Air fuel ratio sensor	B

   Lean: During the Control the Injection Volume for A/F Sensor Active Test, the air fuel ratio sensor output voltage (AFS Voltage) is consistently higher than 3.4 V, and the heated oxygen sensor output voltage (O2S) is consistently below 0.4 V.
   Rich: During the Control the Injection Volume for A/F Sensor Active Test, the AFS Voltage is consistently below 3.1 V, and the O2S is consistently higher than 0.55 V.
   Lean/Rich: During the Control the Injection Volume for A/F Sensor Active Test, the output voltage of the heated oxygen sensor alternates correctly.
   

   HINT:

   Refer to "Data List / Active Test" [AFS Voltage B1S1 and O2S B1S2] (HILUX_TGN26 RM000000SXS056X.html).

1. Connect the intelligent tester to the DLC3.
   

2. Turn the ignition switch to ON.
   

3. Turn the intelligent tester on.
   

4. Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / Coolant Temp.
   

5. Read Coolant Temp twice, when the engine is both cold and warmed up.
   

   Standard:

   With cold engine: Same as ambient air temperature.
   With warm engine: Between 75°C and 100°C (167°F and 212°F).
   

1. Connect the intelligent tester to the DLC3.
   

2. Turn the ignition switch to ON.
   

3. Turn the intelligent tester on.
   

4. Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / MAF and Coolant Temp.
   

5. Allow the engine to idle until Coolant Temp reaches 75°C (167°F) or higher.
   

6. Read MAF with the engine speed at 2500 rpm.
   

   Standard:

   Between 4 gm/s and 15 gm/s (shift lever: N; A/C: Off).
   

1. Check the fuel pressure (HILUX_TGN26 RM000000YL703AX_01_0002.html).
   

1. Check for exhaust gas leaks.
   

   OK:

   No gas leaks.
   

1. Perform a spark test (HILUX_TGN26 RM000000SM604YX_02_0001.html).
   

   CAUTION:

   Always disconnect all the fuel injector connectors.

   NOTICE:

   Do not crank the engine for more than 2 seconds.

   OK:

   Spark jumps across electrode gap.
   

1. Inspect the fuel injector assembly (injection and volume) (HILUX_TGN26 RM000000WQQ076X.html).
   

1. Inspect the air fuel ratio sensor (HILUX_TGN26 RM00000142100ZX_01_0001.html).
   

1. Disconnect the air fuel ratio sensor connector.
   

2. Turn the ignition switch to ON.
   

3. Measure the voltage according to the value(s) in the table below.
   

   Standard Voltage:

   Tester Connection	Switch Condition	Specified Condition
   C85-2 (+B) - Body ground	Ignition switch ON	11 to 14 V

   Text in Illustration

   *a	Front view of wire harness connector (to Air Fuel Ratio Sensor)

1. Disconnect the air fuel ratio sensor connector.
   

2. Disconnect the ECM connector.
   

3. Measure the resistance according to the value(s) in the table below.
   
   

   Standard Resistance:

   
   

   Tester Connection	Condition	Specified Condition
   C85-1 (HA1A) - C75-1 (HA1A)	Always	Below 1 Ω
   C85-3 (A1A+) - C75-21 (A1A+)	Always	Below 1 Ω
   C85-4 (A1A-) - C75-31 (A1A-)	Always	Below 1 Ω
   C85-1 (HA1A) or C75-1 (HA1A) - Body ground	Always	10 kΩ or higher
   C85-3 (A1A+) or C75-21 (A1A+) - Body ground	Always	10 kΩ or higher
   C85-4 (A1A-) or C75-31 (A1A-) - Body ground	Always	10 kΩ or higher

1. Replace the air fuel ratio sensor (HILUX_TGN26 RM00000142300YX.html).
   

1. Connect the intelligent tester to the DLC3.
   

2. Turn the ignition switch to ON.
   

3. Turn the intelligent tester on.
   

4. Clear the DTCs (HILUX_TGN26 RM000000PDK0SXX.html).
   

5. Turn the ignition switch off and wait for at least 30 seconds.
   

6. Turn the ignition switch to ON and turn the intelligent tester on.
   

7. Start the engine and warm it up.
   

8. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
   

9. Enter the following menus: Powertrain / Engine and ECT / DTC.
   

10. Read the DTCs.
    
    

    Result

    Result	Proceed to
    DTC P0171 or P0172 is output	A
    DTC is not output	B

1. Check the connection and terminal contact pressure of connectors and wire harnesses between the mass air flow meter and ECM (HILUX_TGN26 RM000004QR6001X.html).
   

   HINT:

   Repair any problems.

1. Connect the intelligent tester to the DLC3.
   

2. Turn the ignition switch to ON.
   

3. Turn the intelligent tester on.
   

4. Clear the DTCs (HILUX_TGN26 RM000000PDK0SXX.html).
   

5. Turn the ignition switch off and wait for at least 30 seconds.
   

6. Turn the ignition switch to ON and turn the intelligent tester on.
   

7. Start the engine and warm it up.
   

8. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
   

9. Enter the following menus: Powertrain / Engine and ECT / DTC.
   

10. Read the DTCs.
    
    

    Result

    Result	Proceed to
    DTC P0171 or P0172 is output	A
    DTC is not output	B

1. Disconnect the mass air flow meter connector.
   

2. Disconnect the ECM connector.
   

3. Measure the resistance according to the value(s) in the table below.
   

   Standard Resistance:

   Tester Connection	Condition	Specified Condition
   C36-3 (VG) - C76-28 (VG)	Always	Below 1 Ω
   C36-2 (E2G) - C76-30 (E2G)	Always	Below 1 Ω
   C36-3 (VG) or C76-28 (VG) - Body ground	Always	10 kΩ or higher

1. Replace the mass air flow meter (HILUX_TGN26 RM000000VW602CX.html).
   

   HINT:

   If the result of the inspection performed in step 6 indicated no problem, proceed to the next step without replacing the mass air flow meter.

1. Connect the intelligent tester to the DLC3.
   

2. Turn the ignition switch to ON.
   

3. Turn the intelligent tester on.
   

4. Clear the DTCs (HILUX_TGN26 RM000000PDK0SXX.html).
   

5. Turn the ignition switch off and wait for at least 30 seconds.
   

6. Turn the ignition switch to ON and turn the intelligent tester on.
   

7. Start the engine and warm it up.
   

8. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
   

9. Enter the following menus: Powertrain / Engine and ECT / DTC.
   

10. Read the DTCs.
    
    

    Result

    Result	Proceed to
    DTC is not output	A
    DTC P0171 or P0172 is output	B

1. Remove the A/F relay from engine room relay block and junction block.
   

2. Disconnect the cable from the positive (+) battery terminal.
   

3. Disconnect the air fuel ratio sensor connector.
   

4. Remove the No. 1 integration relay from the engine room relay block and junction block.
   

5. Measure the resistance according to the value(s) in the table below.
   
   

   Standard Resistance:

   
   

   Tester Connection	Condition	Specified Condition
   A/F relay terminal 5 - Positive (+) battery cable terminal	Always	Below 1 Ω
   A/F relay terminal 1 - 1J-5	Always	Below 1 Ω
   C85-2 (+B) - A/F relay terminal 3	Always	Below 1 Ω
   A/F relay terminal 2 - Body ground	Always	Below 1 Ω
   A/F relay terminal 5 or Positive (+) battery cable terminal - Body ground	Always	10 kΩ or higher
   A/F relay terminal 1 or 1J-5 - Body ground	Always	10 kΩ or higher
   C85-2 (+B) or A/F relay terminal 3 - Body ground	Always	10 kΩ or higher

1. Inspect the A/F relay (HILUX_TGN26 RM000003BLB021X_01_0013.html).