DTC P0171: System Too Lean (Bank 1); DTC P0172: System Too Rich (Bank 1); DTC P0174: System Too Lean (Bank 2); DTC P0175: System Too Rich (Bank 2): Procedure

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch on (IG).
3. Turn the tester on.
4. Select the following menu items: Powertrain / Engine and ECT / Trouble Codes.
5. Read 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.

B → See step   23 

A: Go to next step 

1. Check the PCV hose connections.

   OK

   PCV hose is connected correctly and is not damaged.

NG → REPAIR OR REPLACE PCV HOSE 

OK: Go to next step 

1. Check the air induction system for vacuum leak, refer to ON-VEHICLE INSPECTION .

   OK

   No leak from air induction system.

NG → REPAIR OR REPLACE AIR INDUCTION SYSTEM 

OK: Go to next step 

1. Connect the Techstream to the DLC3.
2. Start the engine.
3. Turn the tester on.
4. Warm up the engine at an engine speed of 2500 RPM for approximately 90 seconds.
5. Select the following menu items: 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 in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).
7. Monitor the voltage outputs of the air fuel ratio sensor and the heated oxygen sensor (AFS Voltage B1 S1 or AFS Voltage B2 S1 and O2S B1 S2 or O2S B2 S2) displayed on the tester.

   HINT: 

   • The Control the Injection Volume for A/F Sensor operation lowers the fuel injection volume by 12.5% or increases the injection volume by 25%.
   • Each sensor reacts in accordance with increases and decreases in the fuel injection volume.

   Standard

   Tester Display	Injection Volume	Status	Voltage
   AFS Voltage B1 S1 AFS Voltage B2 S1 (Air fuel ratio sensor)	+25%	Rich	Less than 3.1 V
   	-12.5%	Lean	More than 3.4 V
   O2S B1 S2 O2S B2 S2 (Heated oxygen)	+25%	Rich	More than 0.55 V
   	-12.5%	Lean	Less than 0.4 V

   RESULT
   
   

   Status AFS B1 S1 AFS B2 S1	Status O2S B1 S2 O2S B2 S2	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 Injector blockage Gas leak from exhaust system Air induction system Fuel pressure Mass air flow meter Engine coolant temperature sensor	A
   Rich	Rich	Actual air fuel ratio rich	-	Injector blockage or blockage Gas leak 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 more than 3.4 V, and the heated oxygen sensor output voltage (O2S) is consistently less than 0.4 V.

   Rich: During Control the Injection Volume for A/F Sensor, the AFS is consistently less than 3.1 V, and the O2S is consistently more 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.

B → See step   11 

A: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch on (IG).
3. Turn the tester on.
4. Select the following menu items: Powertrain / Engine and ECT / Data List / All Data / Coolant Temp.
5. Read the Data List twice, when the engine is both cold and warmed up.

   Standard value

   With cold engine: Same as ambient air temperature.

   With warm engine: 80 to 100°C (176 to 212°F).

NG → See step   24 

OK: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch on (IG).
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine / 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 3000RPM.

   Standard

   Between 10 to 25 g/sec. (shift lever: N; A/C: off).

NG → See step   16 

OK: Go to next step 

1. Check the fuel pressure, refer to ON-VEHICLE INSPECTION .

NG → REPAIR OR REPLACE FUEL SYSTEM 

OK: Go to next step 

1. Check for exhaust gas leaks from the exhaust manifold sub-assembly and exhaust pipe.

   OK

   No gas leak.

NG → REPAIR OR REPLACE EXHAUST SYSTEM 

OK: Go to next step 

HINT: 

• Refer to the ignition system inspection procedure, refer to ON-VEHICLE INSPECTION .
• If the spark plugs or ignition system malfunctions, engine misfire may occur. The misfire count can be read using the Techstream. Select the following menu items: Powertrain / Engine and ECT / Data List / All Data / Cylinder #1 Misfire Rate (to Cylinder #6 Misfire Rate)

NG → REPAIR OR REPLACE IGNITION SYSTEM 

OK: Go to next step 

HINT: 

• Refer to the fuel injector inspection procedure, refer to INSPECTION .
• If the injectors malfunction, engine misfire may occur. The misfire count can be read using the Techstream. Select the following menu items: Powertrain / Engine and ECT / Data List / All Data / Cylinder #1 Misfire Rate (to Cylinder #6 Misfire Rate).

OK → See step   15 

NG → See step   25 

1. Disconnect the air fuel ratio sensor connector.
   Fig 1: Identifying Air Fuel Ratio Sensor Connector

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the resistance according to the value(s) in the table below.

   Standard resistance

   Bank 1 

   Bank 2 

   Tester Connection	Condition	Specified Condition
   1 (HA1A) - 2 (+B)	20°C (68°F)	1.6 to 3.2 Ω
   1 (HA1A) - 4 (A1A-)	Always	10 kΩ or higher

   Tester Connection	Condition	Specified Condition
   1 (HA2A) - 2 (+B)	20°C (68°F)	1.6 to 3.2 Ω
   1 (HA2A) - 4 (A2A-)	Always	10 kΩ or higher

   TEXT IN ILLUSTRATION
   
   

   *1	Bank 1
   *2	Bank 2
   *a	Component without harness connected (Air Fuel Ratio Sensor)

3. Reconnect the air fuel ratio sensor connector.

NG → See step   26 

OK: Go to next step 

1. Disconnect the air fuel ratio sensor connector.
   Fig 2: Identifying Air Fuel Ratio Sensor Connector

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Turn the ignition switch on (IG).
3. Measure the voltage according to the value(s) in the table below.

   Standard voltage

   Bank 1 

   Bank 2 

   Tester Connection	Switch Condition	Specified Condition
   B20-2 (+B) - Body ground	Ignition switch on (IG)	9 to 14 V

   Tester Connection	Switch Condition	Specified Condition
   B19-2 (+B) - Body ground	Ignition switch on (IG)	9 to 14 V

   TEXT IN ILLUSTRATION
   
   

   *1	Bank 1
   *2	Bank 2
   *a	Front view of wire harness connector (to Air Fuel Ratio Sensor)

4. Reconnect the air fuel ratio sensor connector.

NG → See step   21 

OK: Go to next step 

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)

   Bank 1 

   Bank 2 

   Tester Connection	Condition	Specified Condition
   B20-1 (HA1A) - B48-17 (HA1A)	Always	Below 1 Ω

   Tester Connection	Condition	Specified Condition
   B19-1 (HA2A) - B48-19 (HA2A)	Always	Below 1 Ω

   Standard resistance (Check for short)

   Bank 1 

   Bank 2 

   Tester Connection	Condition	Specified Condition
   B20-1 (HA1A) or B48-17 (HA1A) - Body ground	Always	10 kΩ or higher

   Tester Connection	Condition	Specified Condition
   B19-1 (HA2A) or B48-19 (HA2A) - Body ground	Always	10 kΩ or higher

4. Reconnect the ECM connector.
5. Reconnect the air fuel ratio sensor connector.

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Replace the air fuel ratio sensor, refer to COMPONENTS .

NEXT: Go to next step 

Fig 3: Identifying Vehicle Speed Driving Pattern

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch on (IG).
3. Turn the tester on.
4. Clear DTCs, refer to DTC CHECK / CLEAR .
5. Turn the ignition switch off.
6. Turn the ignition switch on (IG) and turn the Techstream 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 / Trouble Codes.
10. Read DTCs.

    Result

    Result	Proceed to
    DTC P0171, P0172, P0174 or P0175 is output	A
    DTC is not output	B

B → END 

A: Go to next step 

1. Check the connection and terminal contact pressure of connectors and wire harness between the mass air flow meter and ECM See step  5.

   HINT: 

   Repair any problems.

NEXT: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch on (IG).
3. Turn the Techstream on.
4. Clear the DTCs, refer to DTC CHECK / CLEAR .
5. Turn the ignition switch off.
6. Turn the ignition switch on (IG) and turn the Techstream 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 / Trouble Codes.
10. Read DTCs.

    Result

    Result	Proceed to
    DTC P0171, P0172, P0174 or P0175 is output	A
    DTC is not output	B

B → END 

A: Go to next step 

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
   B10-5 (VG) - B50-14 (VG)	Always	Below 1 Ω
   B10-4 (E2G) - B50-13 (E2G)	Always	Below 1 Ω
   B10-5 (VG) or B50-14 (VG) - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Replace the mass air flow meter assembly, refer to REMOVAL .

   HINT: 

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

NEXT: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch on (IG).
3. Turn the Techstream on.
4. Clear the DTCs, refer to DTC CHECK / CLEAR .
5. Turn the ignition switch off.
6. Turn the ignition switch on (IG) and turn the Techstream 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 / Trouble Codes.
10. Read DTCs.

    Result

    Result	Proceed to
    DTC is not output	A
    DTC P0171, P0172, P0174 or P0175 is output	B

B → See step   27 

A → END 

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Inspect the A/F relay, refer to INSPECTION .

NG → See step   28 

OK → CHECK ECM POWER SOURCE CIRCUIT