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Home >> Lexus >> 2009 >> SC 430 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System (Diagnostic Codes (P0010 - P0340)) >> SFI System >> 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
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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. CHECK OTHER DTC OUTPUT (IN ADDITION TO DTC P0171, P0172, P0174, P0175) 
    1. Connect the Techstream to the DLC3.
    2. Turn the ignition switch ON and turn the tester ON.
    3. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
    4. Read the DTCs.

      Result

      Display (DTC output) Proceed to
      P0171, P0172, P0174 or P0175 A
      P0171, P0172, P0174 or P0175 and other DTCs B

    B → GO TO RELEVANT DTC CHART 

    A: Go to next step 

  2. CHECK CONNECTION OF PCV HOSE 

    OK

    PCV hose is connected correctly and is not damaged.

    NG → REPAIR OR REPLACE PCV HOSE 

    OK: Go to next step 

  3. CHECK AIR INDUCTION SYSTEM 
    1. Check the air induction system for vacuum leaks.

    NG → REPAIR OR REPLACE AIR INDUCTION SYSTEM 

    OK: Go to next step 

  4. PERFORM ACTIVE TEST USING TECHSTREAM (A/F CONTROL) 
    1. Perform the Active Test Control the Injection Volume for A/F Sensor with the Techstream and check the heated oxygen sensor status.

      Standard voltage

      Heated oxygen sensor reacts in accordance with the increase and decrease of injection volume:

      +25% → Rich output: More than 0.55 V

      -12.5% → Lean output: Less than 0.4 V

      Related DTCs Heated Oxygen Sensor Status A/F Condition and Heated Oxygen Sensor Condition Misfire Main Suspected Trouble Area Go to Step
      B1S1 B1S2 B2S1 B2S2
      N/A L/R L/R L/R L/R Normal None None N/A
      P0171
      P0174      		 L L L L Actual A/F is lean at all cylinders May occur PCV hose, air induction system, fuel pressure, MAF or ECT A
      P0172
      P0175      		 R R R R Actual A/F is rich at all cylinders None Fuel pressure, MAF or ECT
      P0171 L L L/R L/R Actual A/F is lean at bank 1 May occur Spark plug, ignition system, injector or exhaust gas leak B
      P0174 L/R L/R L L Actual A/F is lean at bank 2
      P0172 R R L/R L/R Actual A/F is rich at bank 1 None Spark plug, ignition system or injector C
      P0175 L/R L/R R R Actual A/F is rich at bank 2
      P0171 L R L/R L/R Heated oxygen sensor (bank 1 sensor 1) malfunction None Heated oxygen sensor (bank 1 sensor 1) D
      P0174 L/R L/R L R Heated oxygen sensor (bank 2 sensor 1) malfunction None Heated oxygen sensor (bank 2 sensor 1)
      P0172 R L L/R L/R Heated oxygen sensor (bank 1 sensor 1) malfunction None Heated oxygen sensor (bank 1 sensor 1)
      P0175 L/R L/R R L Heated oxygen sensor (bank 2 sensor 1) malfunction None Heated oxygen sensor (bank 2 sensor 1)

      HINT: 

      L: During Control the Injection Volume for A/F Sensor of the Active Test, the output voltage of the heated oxygen sensor almost always indicates 0.4 V or less (lean).

      R: During Control the Injection Volume for A/F Sensor of the Active Test, the output voltage of the heated oxygen sensor almost always indicates 0.5 V or more (rich).

    D → See step   11 

    C → See step   10 

    B → See step   8 

    A: Go to next step 

  5. READ VALUE USING TECHSTREAM (COOLANT TEMP) 
    1. Connect the Techstream to the DLC3.
    2. Enter the following menus: Powertrain / Engine and ECT / Data List / Coolant Temp.
    3. Read the Coolant Temp value when the engine is cold and warmed up.

      Standard

      ECT when the engine is cold: Same as ambient temperature

      ECT when the engine is warmed up: 75 to 95°C (167 to 203°F)

    NG → REPLACE ENGINE COOLANT TEMPERATURE SENSOR 

    OK: Go to next step 

  6. READ VALUE USING TECHSTREAM (MAF) 
    1. Enter the following menus: Powertrain / Engine and ECT / Data List / MAF.
    2. Allow the engine to idle until the ECT reaches 75°C (167°F).
    3. Read the MAF value at idle RPM.

      Standard

      MAF at idle RPM: 4.6 to 5.6 g/sec. (shift lever is in N position and A/C is OFF)

    NG → REPLACE MASS AIR FLOW METER 

    OK: Go to next step 

  7. CHECK FUEL PRESSURE 
    1. Check the fuel pressure. Refer to ON-VEHICLE INSPECTION - Step 2 .

    NG → REPAIR OR REPLACE FUEL SYSTEM 

    OK: Go to next step 

  8. CHECK FOR EXHAUST GAS LEAKAGE 

    NG → REPAIR OR REPLACE EXHAUST SYSTEM 

    OK: Go to next step 

  9. CHECK FOR SPARK AND IGNITION 

    HINT: 

    If the spark plugs or ignition system malfunction, engine misfire may occur. The misfire counter can be read with the Techstream. Enter the following menus: Powertrain / Engine and ECT / Data List / Misfire / Cylinder #1 Misfire Count to #8.

    NG → REPAIR OR REPLACE IGNITION SYSTEM 

    OK: Go to next step 

  10. INSPECT FUEL INJECTOR 

    HINT: 

    If the injectors are malfunctioning, engine misfire may occur. The misfire counter can be read with the Techstream. Enter the following menus: Powertrain / Engine and ECT / Data List / Misfire / Cylinder #1 Misfire Count to #8.

    NG → REPLACE FUEL INJECTOR 

    OK: Go to next step 

  11. INSPECT HEATED OXYGEN SENSOR 
    Fig 1: Identifying Heated Oxygen Sensor Connector Terminals
    GTY143106Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Disconnect the H9 and H10 sensor connectors.
    2. Measure the resistance of the heated oxygen sensor.

      Standard resistance

      Tester Connection Specified Condition
      1 (HT) - 2 (+B) 11 to 16 Ω
      1 (HT) - 4 (E1) 10 kΩ or higher

    NG → REPLACE HEATED OXYGEN SENSOR 

    OK: Go to next step 

  12. INSPECT EFI RELAY (Marking: EFI) 
    Fig 2: Inspecting EFI Relay
    GTY126004Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Remove the EFI relay from the engine room No. 2 relay block.
    2. Measure the resistance of the EFI relay.

      Standard resistance

      Tester Connection Specified Condition
      3 - 5 10 kΩ or higher
      3 - 5 Below 1 Ω
      (when battery voltage is applied to terminals 1 and 2)

    NG → REPLACE EFI RELAY 

    OK: Go to next step 

  13. CHECK WIRE HARNESS (HEATED OXYGEN SENSOR (SENSOR 1) - ECM) 
    Fig 3: Checking Wire Harness (Heated Oxygen Sensor (Sensor 1) - ECM)
    GTY133442Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Disconnect the H9 and H10 sensor connectors.
    2. Disconnect the E2 and E4 ECM connectors.
    3. Measure the resistance of the wire harness side connectors.

      Standard resistance

      Tester Connection Specified Condition
      H9-1 (HT) - E2-24 (HT1A) Below 1 Ω
      H9-3 (OX) - E2-30 (OX1A) Below 1 Ω
      H10-1 (HT) - E4-5 (HT2A) Below 1 Ω
      H10-3 (OX) - E4-28 (OX2A) Below 1 Ω
      H9-1 (HT) or E2-24 (HT1A) - Body ground 10 kΩ or higher
      H9-3 (OX) or E2-30 (OX1A) - Body ground 10 kΩ or higher
      H10-1 (HT) or E4-5 (HT2A) - Body ground 10 kΩ or higher
      H10-3 (OX) or E4-28 (OX2A) - Body ground 10 kΩ or higher

    NG → REPAIR OR REPLACE HARNESS AND CONNECTOR 

    OK: Go to next step 

  14. REPLACE HEATED OXYGEN SENSOR 

    NEXT: Go to next step 

  15. PERFORM CONFIRMATION DRIVING PATTERN 
    Fig 4: Performing Confirmation Driving Pattern
    GTY145435Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    • (a) Connect the Techstream to the DLC3.
    • (b) Switch the tester from normal mode to check mode. Refer to CHECK MODE PROCEDURE .
    • (c) Allow the engine to idle until the ECT reaches 75°C (167°F).
    • (d) Allow the vehicle to run at 40 km/h (25 mph) or more for 25 seconds or more.
    • (e) Allow the engine to idle for 30 seconds or more.
    • (f) Perform steps (d) and (e) at least 3 times.

      HINT: 

      If a malfunction exists, the MIL will be illuminated on the multi-information display.

      NOTE:

      If the conditions in this test are not strictly followed, you should perform steps (d) and (e).

      If you do not have the Techstream, turn the ignition switch OFF after performing steps (c) and (f), and then perform steps (c) and (f) again.

    • (g) Allow the engine to idle for 30 seconds.

    NEXT → END 

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