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) [08/2015 - 08/2022]: Procedure

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

Result: 

B 

GO TO DTC CHART 

(Refer to DIAGNOSTIC TROUBLE CODE CHART [08/2015 - 08/2016] , or refer to DIAGNOSTIC TROUBLE CODE CHART [08/2016 - 08/2017] , or refer to DIAGNOSTIC TROUBLE CODE CHART [08/2017 - 08/2019] , or refer to DIAGNOSTIC TROUBLE CODE CHART [08/2019 - 08/2020] , or refer to DIAGNOSTIC TROUBLE CODE CHART [08/2020 - 08/2021] , or refer to DIAGNOSTIC TROUBLE CODE CHART [08/2021 - 08/2022] )

Result: 

A 

See step  2

1. Check the PCV hose connections (Refer to PROCEDURE - Step 3 ).

   OK

   PCV hose is connected correctly and is not damaged.

Result: 

NG 

REPAIR OR REPLACE PCV HOSE 

(Refer to REMOVAL [08/2015 - ] )

Result: 

OK 

See step  3

HINT: 

If a malfunction occurs when depressing the brake pedal, inspect the brake booster assembly, as there may be a vacuum leak in the brake booster assembly itself.

1. Check the intake system for vacuum leaks (Refer to PROCEDURE - Step 3 ).

   OK

   No leaks in intake system.

   HINT: 

   Perform "Inspection After Repair" after repairing or replacing the intake system (Refer to INITIALIZATION [08/2015 - ] ).

Result: 

NG 

REPAIR OR REPLACE INTAKE SYSTEM 

Result: 

OK 

See step  4

1. Connect the Techstream to the DLC3.
2. Start the engine.
3. Turn the Techstream on.
4. Warm up the engine and run 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.
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: 

   • Change the fuel injection volume within the range of -12.5% to +12.5%.
   • 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.

   Techstream Display (Sensor)	Injection Volume	Status	Voltage
   AFS Voltage B1S1 or AFS Voltage B2S1 (Air fuel ratio)	+12.5%	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)	+12.5%	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	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 leaks from exhaust system Intake system Fuel pressure Mass air flow meter assembly Manifold absolute pressure sensor Engine coolant temperature sensor EGR valve assembly	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 assembly Manifold absolute pressure sensor Engine coolant temperature sensor	A
   Lean	Lean/Rich	Air fuel ratio sensor malfunction	Air fuel ratio sensor EGR valve assembly	B
   Rich	Lean/Rich	Air fuel ratio sensor malfunction	Air fuel ratio sensor	B

   Lean: During the Control the Injection Volume 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 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 Active Test, the output voltage of the heated oxygen sensor alternates correctly.

   HINT: 

   Refer to "Data List / Active Test" [AFS Voltage B1S1, AFS Voltage B2S1, O2S B1S2 and O2S B2S2] (Refer to DATA LIST / ACTIVE TEST [08/2015 - 08/2018] , or refer to DATA LIST / ACTIVE TEST [08/2018 - 08/2019] , or refer to DATA LIST / ACTIVE TEST [08/2019 - ] ).

Result: 

B 

See step  11

Result: 

A 

See step  5

1. Connect the Techstream to the DLC3.
2. Turn the engine switch on (IG).
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine and ECT / Data List / Coolant Temp.
5. Read 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).

   HINT: 

   Perform "Inspection After Repairs" after replacing the engine coolant temperature sensor (Refer to INITIALIZATION [08/2015 - ] ).

Result: 

NG 

REPLACE ENGINE COOLANT TEMPERATURE SENSOR 

(Refer to REMOVAL [08/2015 - ] )

Result: 

OK 

See step  6

1. Connect the Techstream to the DLC3.
2. Turn the engine switch on (IG).
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine and ECT / Data List / 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 3000 rpm.

   Standard

   Between 18.3 gm/sec. and 25.8 gm/sec. (shift lever: N; A/C: Off).

Result: 

NG 

See step  18

Result: 

OK 

See step  7

1. Check the fuel pressure (Refer to PROCEDURE - Step 2 ).

   HINT: 

   Perform "Inspection After Repair" after repairing or replacing the fuel system (Refer to INITIALIZATION [08/2015 - ] ).

Result: 

NG 

REPAIR OR REPLACE FUEL SYSTEM 

Result: 

OK 

See step  8

1. Check for exhaust gas leaks.

   OK

   No gas leaks.

   HINT: 

   Perform "Inspection After Repair" after repairing or replacing the exhaust system (Refer to INITIALIZATION [08/2015 - ] ).

Result: 

NG 

REPAIR OR REPLACE EXHAUST SYSTEM 

Result: 

OK 

See step  9

See step  8[08/2015 - 08/2017], or see step  27[08/2017 - 08/2018], or refer to PROCEDURE - Step 27 [08/2018 - 08/2019] , or refer to PROCEDURE - Step 8 [08/2019 - ]

Result: 

NG 

REPAIR OR REPLACE IGNITION SYSTEM 

Result: 

OK 

See step  10

1. Check the injection and volume (Refer to PROCEDURE - Step 1 ).

   HINT: 

   Perform "Inspection After Repair" after replacing the fuel injector assembly (Refer to INITIALIZATION [08/2015 - ] ).

Result: 

OK 

See step  15

Result: 

NG 

REPLACE FUEL INJECTOR ASSEMBLY 

(Refer to REMOVAL [08/2015 - ] )

Refer to PROCEDURE - Step 1 [08/2015 - 08/2018] , or refer to PROCEDURE - Step 1 [08/2018 - ]

Result: 

NG 

REPLACE AIR FUEL RATIO SENSOR 

(Refer to REMOVAL [08/2015 - ] )

Result: 

OK 

See step  12

Refer to PROCEDURE - Step 2 [08/2015 - 08/2018] , or refer to PROCEDURE - Step 2 [08/2018 - ]

Result: 

NG 

See step  23

Result: 

OK 

See step  13

Refer to PROCEDURE - Step 1 [08/2015 - 08/2017] , or refer to PROCEDURE - Step 1 [08/2017 - 08/2022]

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  14

1. Replace the air fuel ratio sensor (Refer to REMOVAL [08/2015 - ] ).

   HINT: 

   Perform "Inspection After Repair" after replacing the air fuel ratio sensor (Refer to INITIALIZATION [08/2015 - ] ).

Result: 

NEXT 

See step  15

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 [08/2015 - ] ).
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 the DTCs.
    RESULT
    
    

    Result	Proceed to
    P0171, P0172, P0174 or P0175 is output	A
    No output	B

Result: 

B 

END 

Result: 

A 

See step  16

1. Connect the Techstream to the DLC3.
2. Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher.

   HINT: 

   • When performing the Active Test, make sure the shift lever is in P or N.
   • The A/C switch and all accessory switches should be off.
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the EGR Step Position.
5. Confirm that Throttle Idle Position is ON and check the engine idling condition and the value of MAP in the Data List while performing the Active Test.

   HINT: 

   • 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.

   OK

   MAP and idling condition change in response to EGR step position as follows.

   Standard

   -	EGR Step Position (Active Test)
   	Step 0	Step 0 to 30
   Idling condition	Steady idling	Idling changes from steady to rough idling or engine stalls
   MAP (Data List)	20 to 40 kPa (150 to 300 mmHg)	MAP value is at least 10 kPa (75 mmHg) higher than when EGR valve is fully closed

Result: 

OK 

See step  18

Result: 

NG 

See step  17

1. Remove the EGR valve assembly (Refer to REMOVAL [08/2015 - ] ).
2. Check if the EGR valve is stuck open.

   OK

   EGR valve is tightly closed.

   HINT: 

   Perform "Inspection After Repairs" after replacing the EGR valve assembly (Refer to INITIALIZATION [08/2015 - ] ).

Result: 

NG 

REPLACE EGR VALVE ASSEMBLY 

(Refer to REMOVAL [08/2015 - ] )

Result: 

OK 

See step  18

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 [08/2015 - ] ).

   HINT: 

   Repair any problems.

Result: 

NEXT 

See step  19

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 [08/2015 - ] ).
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 the DTCs.
    RESULT
    
    

    Result	Proceed to
    P0171, P0172, P0174 or P0175 is output	A
    No output	B

Result: 

B 

END 

Result: 

A 

See step  20

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
   C27-3 (VG) - C29-14 (VG)	Always	Below 1 Ω
   C27-2 (E2G) - C29-13 (E2G)	Always	Below 1 Ω
   C27-3 (VG) or C29-14 (VG) - Body ground	Always	10 kΩ or higher

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  21

1. Replace the mass air flow meter assembly (Refer to REMOVAL [08/2015 - ] ).

   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.
   • Perform "Inspection After Repair" after replacing the mass air flow meter assembly (Refer to INITIALIZATION [08/2015 - ] ).

Result: 

NEXT 

See step  22

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 [08/2015 - ] ).
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 the DTCs.
    RESULT
    
    

    Result	Proceed to
    No output	A
    P0171, P0172, P0174 or P0175 is output	B

Result: 

A 

END 

Result: 

B 

REPLACE ECM 

(Refer to REMOVAL [08/2015 - ] )

Refer to PROCEDURE - Step 6 [08/2015 - 08/2018] , or refer to PROCEDURE - Step 6 [08/2018 - ]

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  24

1. Inspect the No. 1 integration relay (A/F) (Refer to PROCEDURE - Step 4 ).

Result: 

OK 

CHECK ECM POWER SOURCE CIRCUIT 

(Refer to ECM Power Source Circuit [08/2015 - 08/2019] , or refer to ECM Power Source Circuit [08/2019 - ] )

Result: 

NG 

REPLACE NO. 1 INTEGRATION RELAY 

(Refer to PROCEDURE - Step 2 )