DTC P0401: Exhaust Gas Recirculation Flow Insufficient Detected: Procedure

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 / DTC.
5. Read the DTCs.
   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, perform troubleshooting for those DTCs first.

B → See step   12 

A: Go to next step 

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 the Throttle Idle Position is ON and check the engine idling condition and MAP values 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)
   	0 Steps	0 to 30 Steps
   Idling condition	Steady idling	Idling changes from steady to rough idling or engine stall
   MAP (Data List)	-	MAP value is at least +10 kPa (75 mmHg) higher than when EGR valve is fully closed

NG → See step   4 

OK: Go to next step 

1. Confirm that there are no deposits on the EGR valve.
2. Confirm that the EGR valve is closed.

   OK

   There are no deposits and the valve is closed.

NG → See step   4 

OK → See step   5 

1. Replace the EGR valve assembly, refer to REMOVAL .

NEXT: Go to next step 

Fig 1: Check For Deposit

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Check for exhaust leaks at each connection point.
2. Check for cracks, damage and blockage of the pipes between the intake manifold converter and EGR valve assembly.

   HINT: 

   This check may require the removal of components.

3. Check for blockage due to deposits in the EGR valve and pipes.

   OK

   No deposits.

NG → REPAIR OR REPLACE MALFUNCTIONING PARTS 

OK: Go to next step 

Fig 2: Exhaust Leaks At Each Connection Point

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Check for exhaust leaks at each connection point.
2. Check for cracks, damage and blockage of the pipes between the exhaust manifold converter and EGR valve assembly.

   HINT: 

   This check may require the removal of components.

3. Check for blockage due to deposits in the EGR valve and pipes.

   OK

   No deposits.

NG → REPAIR OR REPLACE MALFUNCTIONING PARTS 

OK: Go to next step 

1. Check for blockage in the EGR cooler.

NG → See step   13 

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 / MAP.
5. Read the MAP value.

   Standard

   Switch Condition	Techstream Display
   Ignition switch ON	80 to 110 kPa (600 to 825 mmHg)

6. Read the MAP value when racing the engine.

   Standard

   Engine Condition	Techstream Display
   Idling	20 to 40 kPa (150 to 300 mmHg)

NG → See step   9 

OK → See step   11 

1. Check the intake system for vacuum leaks, refer to ON-VEHICLE INSPECTION - Step 3 .

   OK

   No leaks in intake system.

NG → See step   14 

OK: Go to next step 

1. Replace the manifold absolute pressure sensor, refer to REMOVAL .

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 DTC, 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 until the engine coolant temperature reaches 75°C (167°F) or more.

   HINT: 

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

8. Drive the vehicle at 60 km/h (37 mph) for 5 minutes or more.
   WARNING:

   Strictly observe speed limits and traffic laws when performing the confirmation drive pattern.

9. Idle the engine for 30 seconds or more.
10. Drive the vehicle at 60 km/h (37 mph).
    WARNING:

    Strictly observe speed limits and traffic laws when performing the confirmation drive pattern.

11. Perform fuel cut operation for 5 seconds or more with the accelerator pedal fully released.

    HINT: 

    If the deceleration was not completed, perform the Confirmation Driving Pattern again.

12. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes / Pending.
13. Read the pending DTCs.
14. If a pending DTC is output, the system is malfunctioning.

    HINT: 

    If a pending DTC is not output, perform the following procedure.

15. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
16. Input the DTC: P0401.
17. 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

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