DTC P0171: System Too Lean (Bank 1) (FROM 12/2010); DTC P0172: System Too Rich (Bank 1) (FROM 12/2010); DTC P0174: System Too Lean (Bank 2) (FROM 12/2010); DTC P0175: System Too Rich (Bank 2) (FROM 12/2010): Procedure

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON.
3. Turn the Techstream on.
4. Select the following menu items: Powertrain / Engine / Trouble Codes.
5. Read the DTCs.

   Result

   Result	Proceed to
   DTC P0171, P0172, P0174 or P0175 are output	A
   DTC 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 → REPAIR OR REPLACE PCV HOSE 

OK: Go to next step 

1. Check the air induction system for vacuum leakage.

   OK

   No leakage from the air induction system.

NG → REPAIR OR REPLACE AIR INDUCTION SYSTEM 

OK: Go to next step 

1. Connect 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. Select the following menu items on the Techstream: Powertrain / Engine / 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 in an idling condition (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.

   Standard Voltage

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

   Result

   Status AFS Voltage B1S1 or AFS Voltage B2S1	Status O2S B1S2 or O2S B2S2	A/F Condition and A/F 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 leakage 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 leakage 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 the 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 Techstream to the DLC3.
2. Turn the ignition switch to ON and turn the Techstream on.
3. Select the following menu items: Powertrain / Engine / 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 95°C (167°F and 203°F)

NG → REPLACE ENGINE COOLANT TEMPERATURE SENSOR 

OK: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON.
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine / Data List / All Data / MAF and Coolant Temp.
5. Start the engine and warm it up.
6. Allow the engine to idle until Coolant Temp reaches 75°C (167°F) or higher.
7. Read MAF with the engine speed at 3000 rpm.

   Standard

   Between 12 g/sec. and 17 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 - Step 2 .

NG → REPAIR OR REPLACE FUEL SYSTEM 

OK: Go to next step 

1. Check for exhaust gas leaks.

   OK

   No gas leakage.

NG → REPAIR OR REPLACE EXHAUST SYSTEM 

OK: Go to next step 

1. Check for sparks and ignition. Refer to ON-VEHICLE INSPECTION .

   HINT: 

   If the spark plugs or ignition system malfunction, engine misfire may occur. The misfire count can be read using Techstream. Select the following menu items: Powertrain / Engine / Data List / All Data / Cylinder #1 Misfire Count (to Cylinder #6 Misfire Count).

NG → REPAIR OR REPLACE IGNITION SYSTEM 

OK: Go to next step 

1. Inspect the fuel injector assembly. Refer to INSPECTION .

   HINT: 

   If the injectors malfunction, engine misfire may occur. The misfire count can be read using Techstream. Select the following menu items: Powertrain / Engine / Data List / All Data / Cylinder #1 Misfire Count (to Cylinder #6 Misfire Count).

OK → See step   15 

NG → See step   24 

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 (Bank 1 Sensor 1)

   Standard Resistance (Bank 2 Sensor 1) 

   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

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

3. Reconnect the A/F sensor connector.

NG → See step   25 

OK: Go to next step 

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.

   Standard Resistance (Check for Open)

   Tester Connection	Condition	Specified Condition
   B32-1 (HA1A) - B50-86 (HA1A)	Always	Below 1 Ω
   B32-3 (A1A+) - B50-93 (A1A+)	Always	Below 1 Ω
   B32-4 (A1A-) - B50-116 (A1A-)	Always	Below 1 Ω
   B26-1 (HA2A) - B50-109 (HA2A)	Always	Below 1 Ω
   B26-3 (A2A+) - B50-120 (A2A+)	Always	Below 1 Ω
   B26-4 (A2A-) - B50-119 (A2A-)	Always	Below 1 Ω

   Standard Resistance (Check for Short)

   Tester Connection	Condition	Specified Condition
   B32-1 (HA1A) or B50-86 (HA1A) - Body ground	Always	10 kΩ or higher
   B32-3 (A1A+) or B50-93 (A1A+) - Body ground	Always	10 kΩ or higher
   B32-4 (A1A-) or B50-116 (A1A-) - Body ground	Always	10 kΩ or higher
   B26-1 (HA2A) or B50-109 (HA2A) - Body ground	Always	10 kΩ or higher
   B26-3 (A2A+) or B50-120 (A2A+) - Body ground	Always	10 kΩ or higher
   B26-4 (A2A-) or B50-119 (A2A-) - Body ground	Always	10 kΩ or higher

4. Reconnect the ECM connector.
5. Reconnect the A/F sensor connector.

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Replace the air fuel ratio sensor. Refer to REMOVAL .

NEXT: Go to next step 

1. Connect Techstream to the DLC3.
2. Turn the ignition switch to ON and turn the Techstream on.
3. Clear the DTCs. Refer to DTC CHECK / CLEAR .
4. Turn the ignition switch off and wait for 30 seconds.
5. Turn the ignition switch to ON and turn the Techstream on.
6. Start the engine and warm it up.
7. Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.
8. Select the following menu items: Powertrain / Engine / Trouble Codes / Pending.
9. Read the pending DTCs.

   Result

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

B → See step   16 

A → END 

1. Check the connection and terminal contact pressure of connectors and wire harnesses between the mass air flow meter and ECM. Refer to ELECTRONIC CIRCUIT INSPECTION PROCEDURE .

   HINT: 

   Repair any problems.

NEXT: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON.
3. Turn the Techstream on.
4. Clear the DTCs. Refer to DTC CHECK / CLEAR .
5. Turn the ignition switch off and wait for 30 seconds.
6. Turn the ignition switch to ON 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 / Pending.
10. Read the pending 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
   B50-72 (VG) - B10-5 (VG)	Always	Below 1 Ω
   B50-73 (E2G) - B10-4 (E2G)	Always	Below 1 Ω
   B50-72 (VG) or B10-5 (VG) - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR (MASS AIR FLOW METER - ECM) 

OK: Go to next step 

1. Replace the mass air flow meter.

   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.

NEXT: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON.
3. Turn the Techstream on.
4. Clear the DTCs. Refer to DTC CHECK / CLEAR .
5. Turn the ignition switch off and wait for 30 seconds.
6. Turn the ignition switch to ON 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 / Pending.
10. Read the pending DTCs.
    RESULT
    
    

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

B → See step   26 

A → END 

1. Disconnect the air fuel ratio sensor connector.
2. Remove the engine room junction block from the engine room R/B.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance (Check for Open)

   Tester Connection	Condition	Specified Condition
   B32-2 (+B) - 1C-6	Always	Below 1 Ω
   B26-2 (+B) - 1C-6	Always	Below 1 Ω

   Standard Resistance (Check for Short)

   Tester Connection	Condition	Specified Condition
   B32-2 (+B) or 1C-6 - Body ground	Always	10 kΩ or higher
   B26-2 (+B) or 1C-6 - Body ground	Always	10 kΩ or higher

4. Reinstall the engine room junction block.
5. Reconnect the air fuel ratio sensor connector.

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR (AIR FUEL RATIO SENSOR - ENGINE ROOM JUNCTION BLOCK) 

OK: Go to next step 

NG → REPLACE ENGINE ROOM JUNCTION BLOCK 

OK → See step   27