Dtc P0171 System Too Lean (Bank 1)

DESCRIPTION

MONITOR DESCRIPTION

WIRING DIAGRAM

INSPECTION PROCEDURE

CHECK FOR ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0171, P0172, P0174 OR P0175)

CHECK PCV HOSE CONNECTIONS

CHECK AIR INDUCTION SYSTEM

PERFORM ACTIVE TEST USING GTS (AIR FUEL RATIO CONTROL)

READ VALUE USING GTS (COOLANT TEMP)

INSPECT MASS AIR FLOW METER

CHECK FUEL PRESSURE

CHECK FOR EXHAUST GAS LEAK

CHECK SPARK AND IGNITION

INSPECT FUEL INJECTOR ASSEMBLY (INJECTION AND VOLUME)

INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

INSPECT NO. 1 INTEGRATION RELAY (A/F)

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

REPLACE AIR FUEL RATIO SENSOR

PERFORM CONFIRMATION DRIVING PATTERN

CHECK WHETHER DTC OUTPUT RECURS (DTC P0171, P0172, P0174 OR P0175)

DESCRIPTION

HINT:

1. When DTC P0171 or P0174 is stored, the actual air fuel ratio is on the lean side. When DTC P0172 or P0175 is stored, the actual air fuel ratio is on the rich side.
   
2. If the vehicle runs out of fuel, the air fuel ratio becomes lean and DTC P0171 or P0174 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

WIRING DIAGRAM

INSPECTION PROCEDURE

HINT:

Malfunctioning areas can be identified by performing the Control the Injection Volume for air fuel ratio sensor function provided in the Active Test. The Control the Injection Volume for A/F Sensor function can help to determine whether the air fuel ratio sensor, heated oxygen sensor and other potential trouble areas are malfunctioning.

The following instructions describe how to conduct the Control the Injection Volume for A/F Sensor operation using the GTS.

1. Connect the GTS to the DLC3.
   
2. Start the engine and turn the GTS on.
   
3. Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
   
4. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.
   
5. Perform the Active Test operation with the engine idling (press the RIGHT or LEFT button to change the fuel injection volume).
   
6. Monitor the output voltages of the air fuel ratio sensor and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2, or AFS Voltage B2S1 and O2S B2S2) displayed on the GTS.
   

HINT:

1. The Control the Injection Volume for A/F Sensor operation lowers the fuel injection volume by 12.5% or increases the injection volume by 12.5%.
   
2. Each sensor reacts in accordance with increases and decreases in the fuel injection volume.
   

NOTICE:

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.

Case	Air fuel ratio sensor (Sensor 1) Output Voltage	Heated oxygen sensor (Sensor 2) Output Voltage	Main Suspected Trouble Area
1			-
2			Air fuel ratio sensor Air fuel ratio sensor heater Air fuel ratio sensor circuit
3			Heated oxygen sensor Heated oxygen sensor heater Heated oxygen sensor circuit
4			Fuel injector assembly Fuel pressure Gas leakage from exhaust system (Air fuel ratio extremely rich or lean)

1. Following the Control the Injection Volume for A/F Sensor procedure enables technicians to check and graph the voltage outputs of both the air fuel ratio and heated oxygen sensors.
   
2. To display the graph, enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / A/F Control System / AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2.
   

HINT:

1. Read freeze frame data using the GTS. 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.
   

1. Connect the GTS to the DLC3.
   

2. Turn the engine switch on (IG) and turn the GTS on.
   

3. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
   

4. Read the DTCs.
   
   

   Result

   Result	Proceed to
   P0171, P0172, P0174 or P0175	A
   P0171, P0172, P0174 or P0175 and other DTCs	B

   HINT:

   If any DTCs other than P0171, P0172, P0174 or P0175 are output, troubleshoot those DTCs first.

1. Check the PCV hose connections.
   

   OK:

   PCV hose is connected correctly and is not damaged.
   

HINT:

If a malfunction occurs when depressing the brake pedal, inspect the brake booster assembly, as there may be a vacuum leak in the brake booster assembly itself

1. Check the air induction system for vacuum leakage.
   

   OK:

   No leakage in air induction system.
   

   HINT:

   for Automatic Transmission

   Perform "Inspection After Repair" after repairing or replacing the intake system (LandCruiser RM000004NJC03SX.html).

1. Connect the GTS to the DLC3.
   

2. Start the engine and turn the GTS on.
   

3. Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
   

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

5. Perform the Control the Injection Volume for A/F Sensor operation with the engine idling (press the RIGHT or LEFT button to change the fuel injection volume).
   

6. Monitor the voltage outputs of the air fuel ratio and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2, or AFS Voltage B2S1 and O2S B2S2) displayed on the GTS.
   

   HINT:

   1. The Control the Injection Volume for A/F Sensor operation lowers the fuel injection volume by 12.5% or increases the injection volume by 12.5%.
      
   2. Each sensor reacts in accordance with increases and decreases in the fuel injection volume.
      
   
   

   Standard:

   
   

   GTS Display (Sensor)	Injection Volume	Status	Voltage
   AFS Voltage B1S1 or AFS Voltage B2S1 (Air fuel ratio sensor)	+12.5%	Rich	Below 3.1 V
   AFS Voltage B1S1 or AFS Voltage B2S1 (Air fuel ratio sensor)	-12.5%	Lean	Higher than 3.4 V
   O2S B1S2 or O2S B2S2 (Heated oxygen sensor)	+12.5%	Rich	Higher than 0.55 V
   O2S B1S2 or O2S B2S2 (Heated oxygen sensor)	-12.5%	Lean	Below 0.4 V

   
   

   Result

   Status of AFS Voltage B1S1 or AFS Voltage B2S1	Status of O2S B1S2 or O2S B2S2	Air fuel ratio Condition and Air fuel ratio Sensor Condition	Misfire	Suspected Trouble Area	Proceed to
   Lean/Rich	Lean/Rich	Normal	-	-	C
   Lean	Lean	Actual air fuel ratio lean	May occur	PCV valve and hose PCV hose connections Fuel injector assembly blockage Gas leakage from exhaust system Air induction system Fuel pressure Mass air flow meter Engine coolant temperature sensor	A
   Rich	Rich	Actual air fuel ratio rich	-	Fuel injector assembly leakage blockage or blockage Gas leakage from exhaust system Ignition system Fuel pressure Mass air flow meter Engine coolant temperature sensor
   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

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

1. Connect the GTS to the DLC3.
   

2. Turn the engine switch on (IG) and turn the GTS on.
   

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

4. Read the Data List twice, when the engine is cold and when it is warmed up.
   

   Standard:

   With cold engine: Same as ambient air temperature.
   With warm engine: 80 to 100°C (176 to 212°F).
   

   HINT:

   for Automatic Transmission

   Perform "Inspection After Repair" after replacing the engine coolant temperature sensor (LandCruiser RM000004NJC03SX.html).

1. Inspect the mass air flow meter (LandCruiser RM000002PPR02RX.html).
   

   HINT:

   for Automatic Transmission

   Perform "Inspection After Repair" after replacing the mass air flow meter subassembly (LandCruiser RM000004NJC03SX.html).

1. Check the fuel pressure (LandCruiser RM000000YL706HX_01_0002.html).
   

1. Inspect for exhaust gas leakage from the exhaust manifold sub-assembly and exhaust pipes.
   

   OK:

   No gas leakage.
   

   HINT:

   for Automatic Transmission

   Perform "Inspection After Repair" after repairing or replacing the exhaust system (LandCruiser RM000004NJC03SX.html).

1. Check the ignition system (LandCruiser RM000000SM6078X_02_0001.html).
   

   HINT:

   1. If the spark plugs or ignition system malfunctions, engine misfires may occur. The misfire count can be read using the GTS. Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / Cylinder #1 Misfire Rate (to Cylinder #6 Misfire Count).
      
   for Automatic Transmission
   1. Perform "Inspection After Repair" after repairing or replacing the ignition system (LandCruiser RM000004NJC03SX.html).
      

1. Inspect the fuel injector assembly (LandCruiser RM000000WQQ0BHX.html).
   

   HINT:

   1. If the injectors malfunction, engine misfires may occur. The misfire count can be read using the GTS. Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / Cylinder #1 Misfire Rate (to Cylinder #6 Misfire Count).
      
   for Automatic Transmission
   1. Perform "Inspection After Repair" after replacing the fuel injector assembly (LandCruiser RM000004NJC03SX.html).
      

1. Inspect the air fuel ratio sensor (LandCruiser RM000002RV202KX_01_0001.html).
   

   HINT:

   for Automatic Transmission

   Perform "Inspection After Repair" after replacing the air fuel ratio sensor (LandCruiser RM000004NJC03SX.html).

1. Inspect the No. 1 integration relay (A/F) (LandCruiser RM000003BLB03QX_01_0015.html).
   

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 (Check for Open):

   for Automatic Transmission

   Tester Connection	Condition	Specified Condition
   C25-1 (HA1A) - C37-17 (HA1A)	Always	Below 1 Ω
   C26-1 (HA2A) - C37-12 (HA2A)	Always	Below 1 Ω

   for Manual Transmission

   Tester Connection	Condition	Specified Condition
   C25-1 (HA1A) - C37-17 (HA1A)	Always	Below 1 Ω
   C26-1 (HA2A) - C37-19 (HA2A)	Always	Below 1 Ω

   
   

   Standard Resistance (Check for Short):

   for Automatic Transmission

   Tester Connection	Condition	Specified Condition
   C25-1 (HA1A) or C37-17 (HA1A) - Body ground	Always	10 kΩ or higher
   C26-1 (HA2A) or C37-12 (HA2A) - Body ground	Always	10 kΩ or higher

   for Manual Transmission

   Tester Connection	Condition	Specified Condition
   C25-1 (HA1A) or C37-17 (HA1A) - Body ground	Always	10 kΩ or higher
   C26-1 (HA2A) or C37-19 (HA2A) - Body ground	Always	10 kΩ or higher

4. Reconnect the air fuel ratio sensor connector.
   

5. Reconnect the ECM connector.
   

1. Replace the air fuel ratio sensor (LandCruiser RM000002W9Q017X.html).
   

   HINT:

   for Automatic Transmission

   Perform "Inspection After Repair" after replacing the air fuel ratio sensor (LandCruiser RM000004NJC03SX.html).

1. Connect the GTS to the DLC3 (step "a").
   

2. Turn the engine switch on (IG) and turn the GTS on (step "b").
   

3. Clear DTCs (LandCruiser RM000000PDK1DIX.html) (step "c").
   

4. Switch the ECM from normal mode to check mode using the GTS (LandCruiser RM000000PDL0Y3X.html) (step "d").
   

5. Start the engine and warm it up with all the accessories switched off (step "e").
   

6. Drive the vehicle at between 60 km/h and 120 km/h (38 mph and 75 mph) and at an engine speed of between 1400 rpm and 3200 rpm for 3 to 5 minutes (step "f").
   

   HINT:

   If the system is still malfunctioning, the MIL is illuminated during this step.

   NOTICE:

   If the conditions in this test are not strictly followed, no malfunction will be detected.

1. Connect the GTS to the DLC3.
   

2. Turn the engine switch on (IG) and turn the GTS on.
   

3. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
   

4. Read the DTCs.
   
   

   Result

   Result	Proceed to
   No output	A
   P0171, P0172, P0174 or P0175	B