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) (08/2010 - 08/2011): Procedure

1. Connect the Techstream to the DLC3.
2. Turn the engine switch on (IG) and turn the Techstream on.
3. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
4. Read DTCs.
   RESULT
   
   

   Result	Proceed to
   P0171, P0172, P0174 or P0175 is output	A
   P0171, P0172, P0174 or P0175 and other DTCs are output	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 → See step   24 

OK: Go to next step 

1. Check the air induction system for vacuum leaks.

   OK

   No leaks from air induction system.

NG → REPAIR OR REPLACE INTAKE SYSTEM 

OK: Go to next step 

1. Connect the Techstream to the DLC3.
2. Start the engine and turn the Techstream 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 A/F and HO2 sensors (AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2) displayed on the Techstream.

   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.
   • The A/F sensor has an output delay of a few seconds and the heated oxygen sensor has a maximum output delay of approximately 20 seconds.

   Standard voltage

   Tester Display (Sensor)	Injection Volumes	Status	Voltages
   AFS Voltage B1S1 or AFS Voltage B2S1 (A/F)	+25%	Rich	Less than 3.1
   	-12.5%	Lean	More than 3.4
   O2S B1S2 or O2S B2S2 (HO2)	+25%	Rich	More than 0.55
   	-12.5%	Lean	Less than 0.4

   RESULT
   
   

   Status AFS Voltage B1S1 or AFS Voltage B2S1	Status O2S B1S2 or O2S B2S2	A/F Condition and A/F Sensor Condition	Misfires	Suspected Trouble Areas	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 (MAF) meter Engine Coolant Temperature (ECT) sensor	A
   Rich	Rich	Actual air-fuel ratio rich	-	Injector leakage or blockage Gas leak from exhaust system Ignition system Fuel pressure MAF meter ECT sensor	A
   Lean	Lean/Rich	A/F sensor malfunction	-	A/F sensor	B
   Rich	Lean/Rich	A/F sensor malfunction	-	A/F sensor	B

   Lean: During Control the Injection Volume for A/F Sensor, the A/F sensor output voltage (AFS) is consistently more than 3.4 V, and the HO2 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 engine switch on (IG) and turn the Techstream on.
3. Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / Coolant Temp.
4. Read the 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).

NG → See step   25 

OK: Go to next step 

1. Inspect the mass air flow meter. Refer to INSPECTION .

NG → See step   26 

OK: Go to next step 

1. Check the fuel pressure. Refer to ON-VEHICLE INSPECTION - Step 2 .

NG → REPAIR OR REPLACE FUEL SYSTEM 

OK: Go to next step 

1. Check for exhaust gas leaks.

   OK

   No gas leaks.

NG → REPAIR OR REPLACE EXHAUST SYSTEM 

OK: Go to next step 

1. Check for sparks and ignition See step  24.

NG → REPAIR OR REPLACE IGNITION SYSTEM 

OK: Go to next step 

1. Check the fuel injector. Refer to INSPECTION .

OK → See step   15 

NG → See step   27 

1. Disconnect the A/F sensor connector.
   Fig 1: Identifying A/F Sensor Connector Terminals

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   1 (HA1A) - 2 (+B)	20°C (68°F)	1.8 to 3.4 Ω
   1 (HA1A) - 4 (A1A-)	Always	10 kΩ or higher
   1 (HA2A) - 2 (+B)	20°C (68°F)	1.8 to 3.4 Ω
   1 (HA2A) - 4 (A2A-)	Always	10 kΩ or higher

NG → See step   28 

OK: Go to next step 

Fig 2: Identifying A/F Sensor Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Disconnect the A/F sensor connector.
2. Turn the engine switch on (IG).
3. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   C47-2 (+B) - Body ground	Engine switch on (IG)	11 to 14 V
   C48-2 (+B) - Body ground	Engine switch on (IG)	11 to 14 V

NG → See step   21 

OK: Go to next step 

1. Disconnect the A/F sensor connector.
2. Disconnect the ECM connector.
3. Measure the resistance according to the value(s) in the table below.
   Fig 3: Identifying C47 And C48 A/F Sensor And C53 ECM Connector Terminals

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   C47-1 (HA1A) - C53-22 (HA1A)	Always	Below 1 Ω
   C47-3 (A1A+) - C53-126 (A1A+)	Always	Below 1 Ω
   C47-4 (A1A-) - C53-125 (A1A-)	Always	Below 1 Ω
   C48-1 (HA2A) - C53-20 (HA2A)	Always	Below 1 Ω
   C48-3 (A2A+) - C53-103 (A2A+)	Always	Below 1 Ω
   C48-4 (A2A-) - C53-102 (A2A-)	Always	Below 1 Ω
   C47-1 (HA1A) or C53-22 (HA1A) - Body ground	Always	10 kΩ or higher
   C47-3 (A1A+) or C53-126 (A1A+) - Body ground	Always	10 kΩ or higher
   C47-4 (A1A-) or C53-125 (A1A-) - Body ground	Always	10 kΩ or higher
   C48-1 (HA2A) or C53-20 (HA2A) - Body ground	Always	10 kΩ or higher
   C48-3 (A2A+) or C53-103 (A2A+) - Body ground	Always	10 kΩ or higher
   C48-4 (A2A-) or C53-102 (A2A-) - Body ground	Always	10 kΩ or higher

   Fig 4: Oxygen (A/F) Sensor System Diagram

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR (A/F SENSOR - ECM) 

OK: Go to next step 

1. Replace the A/F sensor. Refer to REMOVAL .

NEXT: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the engine switch on (IG).
3. Turn the Techstream on.
4. Clear the DTCs. Refer to DTC CHECK / CLEAR .
5. Turn the engine switch off.
6. Turn the engine 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 the Confirmation Driving Pattern.
9. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
10. Input the DTC: P0171, P0172, P0174 or P0175.
11. Check the DTC judgment result.
    RESULT
    
    

    Result	Proceed to
    ABNORMAL (DTC P0171, P0172, P0174 or P0175 is output)	A
    NORMAL (No DTC is output)	B

B → END 

A: Go to next step 

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

   HINT: 

   Repair any problems.

NEXT: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the engine switch on (IG).
3. Turn the Techstream on.
4. Clear the DTCs. Refer to DTC CHECK / CLEAR .
5. Turn the engine switch off.
6. Turn the engine 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
   C3-3 (VG) - C53-74 (VG)	Always	Below 1 Ω
   C3-2 (E2G) - C53-75 (E2G)	Always	Below 1 Ω
   C3-3 (VG) or C53-74 (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 in 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 engine switch on (IG).
3. Turn the Techstream on.
4. Clear the DTC. Refer to DTC CHECK / CLEAR .
5. Turn the engine switch off.
6. Turn the engine 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 the 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   30 

A → END 

Fig 5: Identifying C47 And C48 A/F Sensor And 1A Integration Relay Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Disconnect the A/F sensor connector.
2. Remove the integration relay from the engine room relay block.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   C47-2 (+B) - 1A-4	Always	Below 1 Ω
   C48-2 (+B) - 1A-4	Always	Below 1 Ω
   C47-2 (+B) or 1A-4 - Body ground	Always	10 kΩ or higher
   C48-2 (+B) or 1A-4 - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Remove the integration relay from the engine room relay block.
2. Disconnect the integration connector.
   Fig 6: Identifying Integration Relay Connector Terminals

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   1C-1 - 1A-4	Battery voltage not applied	10 kΩ or higher
   	Battery voltage applied to terminals 1A-2 and 1A-3	Below 1 Ω

NG → REPLACE INTEGRATION RELAY (A/F) 

OK → See step   29