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 to ON and turn the Techstream on.
3. Enter the following menus: Powertrain / Engine and ECT / Trouble Code.
4. Read DTCs.
   RESULT
   
   

   Display (DTC Output)	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   25 

A: Go to next step 

1. Check the PCV hose connections.

   OK

   PCV hose is connected correctly and is not damaged.

NG → See step   26 

OK: Go to next step 

1. Check the air induction system for vacuum leakage.

   OK

   No leakage from air induction system.

NG → See step   27 

OK: Go to next step 

1. Connect the Techstream to the DLC3.
2. Start the engine.
3. Turn the Techstream on.
4. Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
5. Enter the following menus: 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 idling (press the RIGHT or LEFT button to change the fuel injection volume).
7. Monitor the output voltages 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 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 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.

   Techstream Display (Sensor)	Injection Volume	Status	Voltage
   AFS Voltage B1S1 or AFS Voltage B2S1 (Air fuel ratio)	+25%	Rich	Below 3.1 V
   AFS Voltage B1S1 or AFS Voltage B2S1 (Air fuel ratio)	-12.5%	Lean	Higher than 3.4 V
   O2S B1S2 or O2S B2S2 (Heated oxygen)	+25%	Rich	Higher than 0.55 V
   O2S B1S2 or O2S B2S2 (Heated oxygen)	-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	-	-	A
   Lean	Lean	Actual air fuel ratio lean	May occur	PCV valve and hose PCV hose connections Fuel injector assembly blockage Gas leaks from exhaust system Intake system Fuel pressure Mass air flow meter sub-assembly Engine coolant temperature sensor	A
   Rich	Rich	Actual air fuel ratio rich	-	Fuel injector assembly leakage or blockage Gas leaks from exhaust system Ignition system Fuel pressure Mass air flow meter sub-assembly Engine coolant temperature sensor	A
   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	B

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

   Rich: During the Control the Injection Volume for A/F Sensor Active Test, the AFS Voltage is consistently below 3.1 V, and the O2S is consistently higher than 0.55 V.

   Lean/Rich: During the Control the Injection Volume for A/F Sensor 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 to ON and turn the Techstream on.
3. Enter the following menus: Powertrain / Engine and ECT / Data List / Coolant Temp.
4. Read Coolant Temp twice, when the engine is cold and when it is 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   28 

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 and ECT / Data List / All Data / MAF, Coolant Temp and Engine speed.
5. Allow the engine to idle until Coolant Temp reaches 75°C (167°F) or higher.
6. Read MAF with the engine speed at 3000 rpm.

   Standard

   Between 13.8 g/sec. and 17.3 g/sec. (shift lever: N; A/C: Off).

NG → See step   17 

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 leakage.

   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 - Step 1 .

   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 and ECT / 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. Check the fuel injector assembly. Refer to INSPECTION .

   HINT: 

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

OK → See step   15 

NG → See step   29 

NG → See step   30 

OK: Go to next step 

NG → See step   24 

OK: Go to next step 

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 the Techstream to the DLC3.
2. Turn the ignition switch ON.
3. Turn the Techstream on.
4. Clear the DTCs. Refer to DTC CHECK / CLEAR .
5. Turn the ignition switch off and wait for at least 30 seconds.
6. Turn the ignition switch 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 and ECT / Utility / All Readiness.
10. Input the DTC: P0171, P0172, P0174 or P0175.
11. Check the DTC judgment result.
    RESULT
    
    

    Techstream Display	Description
    NORMAL	DTC judgment completed System normal
    ABNORMAL	DTC judgment completed System abnormal
    INCOMPLETE	DTC judgment not completed Perform driving pattern after confirming DTC enabling conditions
    UNKNOWN	Unable to perform DTC judgment Number of DTCs which do not fulfill DTC preconditions has reached ECU's memory limit

NEXT: Go to next step 

1. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
2. Input the DTC: P0171, P0172, P0174 or P0175.
3. Check that DTC MONITOR is NORMAL.
4. Enter the following menus: Powertrain / Engine and ECT / Trouble Code / Pending.
5. Read Pending DTCs.
   RESULT
   
   

   Display (DTC Output)	Proceed to
   P0171, P0172, P0174 or P0175	A
   No 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. 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 ON.
3. Turn the Techstream on.
4. Clear the DTCs. Refer to DTC CHECK / CLEAR .
5. Turn the ignition switch off and wait for at least 30 seconds.
6. Turn the ignition switch 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 and ECT / Utility / All Readiness.
10. Input the DTC: P0171, P0172, P0174 or P0175.
11. Check the DTC judgment result.
    RESULT
    
    

    Techstream Display	Description
    NORMAL	DTC judgment completed System normal
    ABNORMAL	DTC judgment completed System abnormal
    INCOMPLETE	DTC judgment not completed Perform driving pattern after confirming DTC enabling conditions
    UNKNOWN	Unable to perform DTC judgment Number of DTCs which do not fulfill DTC preconditions has reached ECU's memory limit

NEXT: Go to next step 

1. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
2. Input the DTC: P0171, P0172, P0174 or P0175.
3. Check that DTC MONITOR is NORMAL.
4. Enter the following menus: Powertrain / Engine and ECT / Trouble Code / Pending.
5. Read Pending DTCs.
   RESULT
   
   

   Display (DTC Output)	Proceed to
   P0171, P0172, P0174 or P0175	A
   No 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
   B35-5 (VG) - B37-14 (VG)	Always	Below 1 Ω
   B35-4 (E2G) - B37-13 (E2G)	Always	Below 1 Ω
   B35-5 (VG) or B37-14 (VG) - Body ground	Always	10 kΩ or higher

4. Reconnect the mass air flow meter connector.
5. Reconnect the ECM connector.

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 ignition switch ON.
3. Turn the Techstream on.
4. Clear the DTCs. Refer to DTC CHECK / CLEAR .
5. Turn the ignition switch off and wait for at least 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 and ECT / Utility / All Readiness.
10. Input the DTC: P0171, P0172, P0174 or P0175.
11. Check the DTC judgment result.
    RESULT
    
    

    Techstream Display	Description
    NORMAL	DTC judgment completed System normal
    ABNORMAL	DTC judgment completed System abnormal
    INCOMPLETE	DTC judgment not completed Perform driving pattern after confirming DTC enabling conditions
    UNKNOWN	Unable to perform DTC judgment Number of DTCs which do not fulfill DTC preconditions has reached ECU's memory limit

NEXT: Go to next step 

1. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
2. Input the DTC: P0171, P0172, P0174 or P0175.
3. Check that DTC MONITOR is NORMAL.
4. Enter the following menus: Powertrain / Engine and ECT / Trouble Code / Pending.
5. Read Pending DTCs.
   RESULT
   
   

   Display (DTC Output)	Proceed to
   No output	A
   P0171, P0172, P0174 or P0175	B

B → See step   31 

A → END 

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → See step   32