LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Lexus >> 2021 >> RX 450h Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System (Diagnostic Codes) (4 Of 8) >> SFI System >> DTC P0401: Exhaust Gas Recirculation Flow Insufficient Detected [10/2015 - 08/2018] >> Procedure
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC P0401: Exhaust Gas Recirculation Flow Insufficient Detected [10/2015 - 08/2018]: Procedure

  1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO P0401) 
    1. Connect the Techstream to the DLC3.
    2. Turn the power switch on (IG).
    3. Turn the Techstream on.
    4. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
    5. Read the DTCs.

      Powertrain > Engine and ECT > Trouble Codes 

      Result

      Result Proceed to
      DTC P0401 is output A
      DTC P0401 and other DTCs are output B

      HINT: 

      If any DTCs other than P0401 are output, troubleshoot those DTCs first.

    Result: 

    B 

    GO TO DTC CHART. Refer to  DIAGNOSTIC TROUBLE CODE CHART [10/2015 - 08/2016]  , or refer to  DIAGNOSTIC TROUBLE CODE CHART [08/2016 - 12/2017]  , or refer to  DIAGNOSTIC TROUBLE CODE CHART [12/2017 - 03/2018]  , or refer to  DIAGNOSTIC TROUBLE CODE CHART [03/2018 - 08/2018] 

    Result: 

    A 

    See step  2

  2. PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE EGR STEP POSITION) 
    1. Connect the Techstream to the DLC3.
    2. Turn the power switch on (IG).
    3. Turn the Techstream on.
    4. Put the engine in inspection mode (maintenance mode).

      Powertrain > Hybrid Control > Utility 

      Tester Display
      Inspection Mode
    5. Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher.

      HINT: 

      The A/C switch and all accessory switches should be off.

    6. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the EGR Step Position / Data List / MAP and Throttle Idle Position.

      Powertrain > Engine and ECT > Active Test 

      Active Test Display
      Control the EGR Step Position
      Data List Display
      MAP
      Throttle Idle Position
    7. Confirm that the Throttle Idle Position is ON and check the MAP value 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.
      • Do not open the EGR valve 30 steps or more during the Active Test.

      OK

      MAP change in response to EGR step position when Throttle Idle Position is ON in Data List.

      Standard

      - EGR Step Position (Active Test)
      0 Steps 0 to 30 Steps
      MAP
      (Data List)      		 (EGR valve is fully closed) MAP value is at least +10 kPa (1.45 psi) higher than when EGR valve is fully closed

      HINT: 

      • While performing the Active Test, if the increase in the value of MAP is small, the EGR valve assembly may be a malfunctioning.
      • Even if the EGR valve assembly is malfunctioning, rough idling or an increase in the value of MAP may occur while performing the Active Test. However, the amount that the value of MAP increases will be smaller than normal. Be sure to return the EGR valve to step 0 when the Active Test is completed.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    See step  4

    Result: 

    OK 

    See step  3

  3. INSPECT EGR VALVE ASSEMBLY 
    1. Remove the EGR valve assembly.

      Refer to REMOVAL [10/2015 - ]

    2. Check for contamination between the EGR valve and housing.

      OK

      EGR valve is closed and no deposits.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    See step  5

    Result: 

    NG 

    See step  4

  4. REPLACE EGR VALVE ASSEMBLY 
    1. Replace the EGR valve assembly.

      Refer to REMOVAL [10/2015 - ]

      HINT: 

      Perform "Inspection After Repair" after replacing the EGR valve assembly.

      Refer to INITIALIZATION [10/2015 - ]

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  5

  5. CHECK FOR DEPOSIT (EXHAUST MANIFOLD - EGR COOLER ASSEMBLY - EGR VALVE ASSEMBLY - INTAKE MANIFOLD) 
    1. Check for exhaust gas leaks at each connection point.
    2. Check for cracks, damage, and clogs in the pipes between the exhaust manifold, the EGR cooler assembly, the EGR valve assembly and the intake manifold.
      GTY627254Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    3. This check may require the removal of components.
    4. Check if there is a built-up of deposits in the EGR valve of pipes.

      OK

      No deposits

      HINT: 

      Perform "Inspection After Repair" after repairing or replacing the exhaust system.

      Refer to INITIALIZATION [10/2015 - ]

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE MALFUNCTIONING PARTS, COMPONENTS AND AREAS 

    Result: 

    OK 

    See step  6

  6. INSPECT EGR COOLER ASSEMBLY 
    1. Check for blockage of the EGR cooler assembly.

      OK

      No blockage.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE EGR COOLER ASSEMBLY. Refer to  REMOVAL [10/2015 - ] 

    Result: 

    OK 

    See step  7

  7. READ VALUE USING TECHSTREAM (MAP) 
    1. Connect the Techstream to the DLC3.
    2. Turn the power switch on (IG).
    3. Turn the Techstream on.
    4. Enter the following menus: Powertrain / Engine and ECT / Data List / MAP.

      Powertrain > Engine and ECT > Data List 

      Tester Display
      MAP
    5. Read the MAP value.
    6. Put the engine in inspection mode (maintenance mode).

      Powertrain > Hybrid Control > Utility 

      Tester Display
      Inspection Mode
    7. Start the engine.
    8. Read the MAP value at idling.

      Standard

      Engine Condition Techstream Display
      Power switch on (IG) 80 to 110 kPa (12 to 16 psi)
      Idling (Not Charge Control) 20 to 40 kPa (3 to 6 psi)

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    See step  10

    Result: 

    NG 

    See step  8

  8. CHECK INTAKE SYSTEM 
    1. Check the intake system for vacuum leaks.

      Refer to PROCEDURE - Step 1 [10/2015 - 12/2017] , or refer to PROCEDURE - Step 1 [12/2017 - ]

      OK

      No leaks in intake system.

      HINT: 

      Perform "Inspection After Repair" after repairing or replacing the intake system.

      Refer to INITIALIZATION [10/2015 - ]

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE INTAKE SYSTEM 

    Result: 

    OK 

    See step  9

  9. REPLACE MANIFOLD ABSOLUTE PRESSURE SENSOR 
    1. Replace the manifold absolute pressure sensor.

      Refer to REMOVAL [10/2015 - ]

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  10

  10. CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED 
    1. Connect the Techstream to the DLC3.
    2. Turn the power switch on (IG).
    3. Turn the Techstream on.
    4. Clear the DTCs.

      Powertrain > Engine and ECT > Clear DTCs 

    5. Turn the power switch off and wait for at least 30 seconds.
    6. Turn the power switch on (IG).
    7. Turn the Techstream on.
    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 / Pending.
    10. Read the pending DTCs.

      Powertrain > Engine and ECT > Trouble Codes 

      HINT: 

      • If a pending DTC is output, the system is malfunctioning.
      • If a pending DTC is not output, perform the following procedure.
    11. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

      Powertrain > Engine and ECT > Utility 

      Tester Display
      All Readiness
    12. Input the DTC: P0401.
    13. 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
      N/A
      • Unable to perform DTC judgment
      • Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    END 

scientia non olet · About LEMON Manuals