DTC P0171-00: System Too Lean Bank 1; DTC P0172-00: System Too Rich Bank 1 [09/2022 - ]: Procedure

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine / Trouble Codes.
5. Read the DTCs.

   Powertrain > Engine > Trouble Codes 

   Result

   Result	Proceed to
   DTC P0171-00 or P0172-00 is output	A
   DTC P0171-00 or P0172-00 and other DTCs are output	B

   HINT: 

   If any DTCs other than P0171-00 or P0172-00 are output, troubleshoot those DTCs first.

Result: 

B 

GO TO DTC CHART 

Refer to DIAGNOSTIC TROUBLE CODE CHART [09/2022 - 09/2024] , or refer to DIAGNOSTIC TROUBLE CODE CHART [09/2024 - ]

Result: 

A 

See step  2

1. Check the PCV hose connections.

   Refer to COMPONENTS [01/2019 - ]

   OK

   PCV valve and hose are connected correctly and are not damaged.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE PCV HOSE 

Result: 

OK 

See step  3

1. Check the intake system for vacuum leaks.

   Refer to ON-VEHICLE INSPECTION [09/2022 - ]

   OK

   No leaks from intake system.

   HINT: 

   Perform "Inspection After Repair" after repairing or replacing the intake system.

   Refer to INITIALIZATION [09/2022 - ]

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE INTAKE SYSTEM 

Result: 

OK 

See step  4

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Put the engine in Inspection Mode (Maintenance Mode).

   Refer to INSPECTION MODE PROCEDURE [06/2018 - ]

   Powertrain > Hybrid Control > Utility 

   Tester Display
   Inspection Mode

5. Start the engine and warm it up until the engine coolant temperature is 75°C (167°F) or higher.
6. Idle the engine for 5 minutes or more with park (P) selected.
7. Enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor / Data List / A/F (O2) Sensor Current B1S1 and O2 Sensor Voltage B1S2.

   Powertrain > Engine > Active Test 

   Active Test Display
   Control the Injection Volume for A/F Sensor

   Data List Display
   A/F (O2) Sensor Current B1S1
   O2 Sensor Voltage B1S2

8. Change the fuel injection volume using the Techstream, and monitor the output voltage of the air fuel ratio sensor (A/F (O2) Sensor Current B1S1) and heated oxygen sensor (O2 Sensor Voltage B1S2) displayed on the Techstream.

   HINT: 

   • The Active Test "Control the Injection Volume for A/F Sensor" can be used to lower the fuel injection volume by 12.5% or increase the injection volume by 12.5%.
   • The air fuel ratio sensor is displayed as A/F (O2) Sensor Current B1S1, and the heated oxygen sensor is displayed as O2 Sensor Voltage B1S2 on the Techstream.
   • 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.
   • If the sensor output voltage does not change (almost no reaction) while performing the Active Test, the sensor may be malfunctioning.

   Standard

   Techstream Display (Sensor)	Injection Volume	Status	Voltage
   A/F (O2) Sensor Current B1S1 (Air fuel ratio)	12.5%	Rich	Below -0.075 mA
   	-12.5%	Lean	Higher than 0.037 mA
   O2 Sensor Voltage B1S2 (Heated oxygen)	12.5%	Rich	Higher than 0.55 V
   	-12.5%	Lean	Below 0.4 V

   Result

   Status A/F (O2) Sensor Current B1S1	Status O2 Sensor Voltage B1S2	Air Fuel Ratio Condition and Air Fuel Ratio Sensor Condition	Suspected Trouble Area	Proceed to
   Lean/Rich	Lean/Rich	Normal	-	A
   Lean	Lean	Actual air fuel ratio lean	PCV valve and hose PCV hose connections Fuel injector assembly blockage Gas leak from exhaust system Intake system Fuel pressure Mass air flow meter sub-assembly Engine coolant temperature sensor EGR valve assembly
   Rich	Rich	Actual air fuel ratio rich	Fuel injector assembly leak or blockage Gas leak from exhaust system Ignition system Fuel pressure Mass air flow meter sub-assembly 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

   1. Lean: While performing the Active Test "Control the Injection Volume for A/F Sensor", the air fuel ratio sensor output voltage (A/F (O2) Sensor Current B1S1) is consistently higher than 0.037 mA, and the heated oxygen sensor output voltage (O2 Sensor Voltage B1S2) is consistently below 0.4 V.
   2. Rich: While performing the Active Test "Control the Injection Volume for A/F Sensor", the air fuel ratio sensor output voltage (A/F (O2) Sensor Current B1S1) is consistently below -0.075 mA, and the heated oxygen sensor output voltage (O2 Sensor Voltage B1S2) is consistently higher than 0.55 V.
   3. Lean/Rich: While performing the Active Test "Control the Injection Volume for A/F Sensor", the output voltage of the fuel ratio sensor (A/F (O2) Sensor Current B1S1) or heated oxygen sensor (O2 Sensor Voltage B1S2) alternates correctly.

   HINT: 

   Refer to "Data List / Active Test" [A/F (O2) Sensor Current B1S1 and O2 Sensor Voltage B1S2].

   Refer to DATA LIST / ACTIVE TEST [09/2022 - 09/2024] , or refer to DATA LIST / ACTIVE TEST [09/2024 - ]

Result: 

B 

See step  13

Result: 

A 

See step  5

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine / Data List / Coolant Temperature.

   Powertrain > Engine > Data List 

   Tester Display
   Coolant Temperature

5. Read the Data List twice, when the engine is both cold and warmed up.

   Standard

   Techstream Display	Condition	Specified Condition
   Coolant Temperature	Cold engine	Same as ambient air temperature
   	Warm engine	Between 75 and 100°C (167 and 212°F)

   HINT: 

   Perform "Inspection After Repair" after replacing the engine coolant temperature sensor.

   Refer to INITIALIZATION [09/2022 - ]

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE E.F.I. ENGINE COOLANT TEMPERATURE SENSOR 

Refer to REMOVAL [09/2022 - 11/2022] , or refer to REMOVAL [11/2022 - ]

Result: 

OK 

See step  6

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Put the engine in Inspection Mode (Maintenance Mode).

   Refer to INSPECTION MODE PROCEDURE [06/2018 - ]

   Powertrain > Hybrid Control > Utility 

   Tester Display
   Inspection Mode

5. Start the engine and warm it up until the engine coolant temperature is 75°C (167°F) or higher.

   HINT: 

   The A/C switch and all accessories should be off.

6. Enter the following menus: Powertrain / Engine / Active Test / Control the EGR Step Position / Data List / Intake Manifold Absolute Pressure and Engine Independent.

   Powertrain > Engine > Active Test 

   Active Test Display
   Control the EGR Step Position

   Data List Display
   Intake Manifold Absolute Pressure
   Engine Independent

7. Confirm that the value of Data List item Engine Independent is "Operate" then check the value of Intake Manifold Absolute Pressure while performing the Active Test.
   NOTE:

   • Do not leave the EGR valve open for 10 seconds or more during the Active Test.
   • Be sure to return the EGR valve to step 0 when the Active Test is completed.
   • Do not open the EGR valve 30 steps or more during the Active Test.

   OK

   The value of Intake Manifold Absolute Pressure changes in response to the EGR step position when the value of Engine Independent is "Operate".

   Standard

   -	Control the EGR Step Position (Active Test)
   	0 Steps	0 to 30 Steps
   Intake Manifold Absolute Pressure (Data List)	(EGR valve is fully closed)	Intake Manifold Absolute Pressure value is at least +10 kPa (1.45 psi) higher than when EGR valve is fully closed

   HINT: 

   • If the value of Data List item Engine Independent is "Not Opr" when the engine is idling, charge control is being performed. Perform the Active Test after charge control is complete ("Operate" is displayed).
   • While performing the Active Test, if the increase in the value of Intake Manifold Absolute Pressure is small, the EGR valve assembly may be malfunctioning.
   • Even if the EGR valve assembly is malfunctioning, rough idling or an increase in the value of Intake Manifold Absolute Pressure may occur while performing the Active Test. However, the amount that the value of Intake Manifold Absolute Pressure increases will be smaller than normal.

   Result

   Proceed to
   OK
   NG

Result: 

OK 

See step  8

Result: 

NG 

See step  7

1. Remove the EGR valve assembly.

   Refer to REMOVAL [09/2022 - 11/2022] , or refer to REMOVAL [11/2022 - ]

2. Check if the EGR valve is stuck open.

   OK

   EGR valve is tightly closed.

   HINT: 

   Perform "Inspection After Repair" after replacing the EGR valve assembly.

   Refer to INITIALIZATION [09/2022 - ]

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE EGR VALVE ASSEMBLY 

Refer to REMOVAL [09/2022 - 11/2022] , or refer to REMOVAL [11/2022 - ]

Result: 

OK 

See step  8

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Put the engine in Inspection Mode (Maintenance Mode).

   Refer to INSPECTION MODE PROCEDURE [06/2018 - ]

   Powertrain > Hybrid Control > Utility 

   Tester Display
   Inspection Mode

5. Start the engine.
6. Enter the following menus: Powertrain / Engine / Data List / Engine Speed, Mass Air Flow Sensor and Coolant Temperature.

   Powertrain > Engine > Data List 

   Tester Display
   Engine Speed
   Mass Air Flow Sensor
   Coolant Temperature

7. Allow the engine to idle until Coolant Temperature is 75°C (167°F) or higher.
8. Read Mass Air Flow Sensor with the engine speed at 2500 rpm.

   HINT: 

   During charge control, the engine speed is set at idle. Therefore, the engine speed will not increase when the accelerator pedal is depressed. In this case, read the Data List after charge control has completed.

   Standard

   Techstream Display	Condition	Specified Condition
   Mass Air Flow Sensor	Engine warmed up Shift position: P A/C: Off Engine Speed: 2500 rpm	Between 4.5 and 8.5 gm/sec

   Result

   Proceed to
   OK
   NG

Result: 

NG 

See step  20

Result: 

OK 

See step  9

1. Check the fuel pressure.

   Refer to PROCEDURE - Step 2

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE FUEL SYSTEM 

Result: 

OK 

See step  10

1. Check for exhaust gas leaks.

   OK

   No gas leaks in exhaust system.

   HINT: 

   Perform "Inspection After Repair" after repairing or replacing the exhaust system.

   Refer to INITIALIZATION [09/2022 - ]

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE EXHAUST SYSTEM 

Result: 

OK 

See step  11

1. Inspect the ignition system.

   Refer to ON-VEHICLE INSPECTION [01/2019 - ]

   HINT: 

   • If the spark plugs or ignition system malfunctions, engine misfire may occur. The misfire count can be read using the Techstream. Enter the following menus: Powertrain / Engine / Data List / Misfire Count Cylinder #1 to Misfire Count Cylinder #4.
   • Perform "Inspection After Repair" after repairing or replacing the ignition system.

     Refer to INITIALIZATION [09/2022 - ]

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE IGNITION SYSTEM 

Result: 

OK 

See step  12

1. Check the injection and volume.

   HINT: 

   • Refer to the fuel injector assembly inspection procedure.

     Refer to INSPECTION [01/2019 - ]

   • If the fuel injector assemblies malfunction, engine misfire may occur. The misfire count can be read using the Techstream. Enter the following menus: Powertrain / Engine / Data List / Misfire Count Cylinder #1 to Misfire Count Cylinder #4.
   • Perform "Inspection After Repair" after replacing the fuel injector assembly.

     Refer to INITIALIZATION [09/2022 - ]

   Result

   Proceed to
   OK
   NG

Result: 

OK 

See step  20

Result: 

NG 

REPLACE FUEL INJECTOR ASSEMBLY 

Refer to REMOVAL [09/2022 - 11/2022] , or refer to REMOVAL [11/2022 - ]

1. Inspect the air fuel ratio sensor.

   Refer to INSPECTION [09/2022 - ]

   HINT: 

   Perform "Inspection After Repair" after replacing the air fuel ratio sensor.

   Refer to INITIALIZATION [09/2022 - ]

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE AIR FUEL RATIO SENSOR 

Refer to REMOVAL [01/2019 - ]

Result: 

OK 

See step  14

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Disconnect the air fuel ratio sensor connector.
2. Turn the power switch on (IG).
3. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   C55-2 (+B) - Body ground	Power switch on (IG)	11 to 14 V

   Result

   Proceed to
   OK
   NG

Result: 

NG 

See step  23

Result: 

OK 

See step  15

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
   C55-1 (HA1A) - C147-28 (HA1A)	Always	Below 1 Ω
   C55-3 (A1A+) - C147-132 (A1A+)	Always	Below 1 Ω
   C55-4 (A1A-) - C147-131 (A1A-)	Always	Below 1 Ω
   C55-1 (HA1A) or C147-28 (HA1A) - Body ground and other terminals	Always	10 kΩ or higher
   C55-3 (A1A+) or C147-132 (A1A+) - Body ground and other terminals	Always	10 kΩ or higher
   C55-4 (A1A-) or C147-131 (A1A-) - Body ground and other terminals	Always	10 kΩ or higher

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  16

1. Replace the air fuel ratio sensor.

   Refer to REMOVAL [01/2019 - ]

   HINT: 

   Perform "Inspection After Repair" after replacing the air fuel ratio sensor.

   Refer to INITIALIZATION [09/2022 - ]

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  17

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Clear the DTCs.

   Powertrain > Engine > Clear DTCs 

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

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  18

1. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
2. Enter the following menus: Powertrain / Engine / Trouble Codes.
3. Read the DTCs.

   Powertrain > Engine > Trouble Codes 

   Result

   Result	Proceed to
   DTCs are not output	A
   DTC P0171-00 or P0172-00 is output	B

Result: 

A 

END 

Result: 

B 

See step  19

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Put the engine in Inspection Mode (Maintenance Mode).

   Refer to INSPECTION MODE PROCEDURE [06/2018 - ]

   Powertrain > Hybrid Control > Utility 

   Tester Display
   Inspection Mode

5. Start the engine.
6. Enter the following menus: Powertrain / Engine / Data List / Engine Speed, Mass Air Flow Sensor and Coolant Temperature.

   Powertrain > Engine > Data List 

   Tester Display
   Engine Speed
   Mass Air Flow Sensor
   Coolant Temperature

7. Allow the engine to idle until Coolant Temperature is 75°C (167°F) or higher.
8. Read Mass Air Flow Sensor with the engine speed at 2500 rpm.

   HINT: 

   During charge control, the engine speed is set at idle. Therefore, the engine speed will not increase when the accelerator pedal is depressed. In this case, read the Data List after charge control has completed.

   Standard

   Techstream Display	Condition	Specified Condition
   Mass Air Flow Sensor	Engine warmed up Shift position: P A/C: Off Engine Speed: 2500 rpm	Between 4.5 and 8.5 gm/sec

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  20

1. Check the connection and terminal contact pressure of connectors and wire harnesses between the mass air flow meter sub-assembly and ECM.

   Refer to ELECTRONIC CIRCUIT INSPECTION PROCEDURE [06/2018 - ]

   HINT: 

   Repair any problems.

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  21

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Clear the DTCs.

   Powertrain > Engine > Clear DTCs 

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

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  22

1. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
2. Enter the following menus: Powertrain / Engine / Trouble Codes.
3. Read the DTCs.

   Powertrain > Engine > Trouble Codes 

   Result

   Result	Proceed to
   DTCs are not output	A
   DTC P0171-00 or P0172-00 is output	B

Result: 

A 

END 

Result: 

B 

See step  27

1. Inspect the EFI-MAIN NO. 2 relay.

   Refer to ON-VEHICLE INSPECTION [09/2022 - ]

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE EFI-MAIN NO. 2 RELAY 

Result: 

OK 

See step  24

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Remove the EFI-MAIN NO. 2 relay from the No. 1 engine room relay block and No. 1 junction block assembly.
2. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   5 (EFI-MAIN NO. 2 relay) - Body ground	Always	11 to 14 V

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR (AUXILIARY BATTERY - EFI-MAIN NO. 2 RELAY) 

Result: 

OK 

See step  25

1. Remove the EFI-MAIN NO. 2 relay from the No. 1 engine room relay block and No. 1 junction block assembly.
2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   1 (EFI-MAIN NO. 2 relay) - Body ground	Always	Below 1 Ω

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  26

1. Remove the EFI-MAIN NO. 2 relay from the No. 1 engine room relay block and No. 1 junction block assembly.
2. Disconnect the air fuel ratio sensor connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   3 (EFI-MAIN NO. 2 relay) - A46-2 (+B)	Always	Below 1 Ω
   3 (EFI-MAIN NO. 2 relay) or A46-2 (+B) - Body ground and other terminals	Always	10 kΩ or higher

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPAIR OR REPLACE HARNESS OR CONNECTOR (EFI-MAIN NO. 1 RELAY - EFI-MAIN NO. 2 RELAY) 

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

1. Disconnect the mass air flow meter sub-assembly 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
   C26-4 (VCC) - C147-108 (VCVG)	Always	Below 1 Ω
   C26-3 (FG) - C147-140 (VG)	Always	Below 1 Ω
   C26-2 (E2G) - C147-107 (E2G)	Always	Below 1 Ω
   C26-4 (VCC) or C147-108 (VCVG) - Body ground and other terminals	Always	10 kΩ or higher
   C26-3 (FG) or C147-140 (VG) - Body ground and other terminals	Always	10 kΩ or higher
   C26-2 (E2G) or C147-107 (E2G) - Body ground and other terminals	Always	10 kΩ or higher

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  28

1. Replace the mass air flow meter sub-assembly.

   Refer to REMOVAL [09/2022 - ]

   HINT: 

   • If the result of the inspection performed in steps 8 and 19 (READ VALUE USING TECHSTREAM (MASS AIR FLOW SENSOR)) indicated no problem, proceed to the next step without replacing the mass air flow meter sub-assembly.
   • Perform "Inspection After Repair" after replacing the mass air flow meter sub-assembly.

     Refer to INITIALIZATION [09/2022 - ]

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  29

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Clear the DTCs.

   Powertrain > Engine > Clear DTCs 

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

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  30

1. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
2. Enter the following menus: Powertrain / Engine / Trouble Codes.
3. Read the DTCs.

   Powertrain > Engine > Trouble Codes 

   Result

   Result	Proceed to
   DTCs are not output	A
   DTC P0171-00 or P0172-00 is output	B

Result: 

A 

END 

Result: 

B 

REPLACE ECM 

Refer to REMOVAL [09/2022 - 11/2022] , or refer to REMOVAL [11/2022 - ]