DTC P0401: Exhaust Gas Recirculation Flow Insufficient Detected: Procedure

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 DTC.

   Result

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

B → See step   12 

A: Go to next step 

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. Refer to INSPECTION MODE PROCEDURE .
5. 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.

6. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the EGR Step Position.
7. 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 Active Test.
   • Be sure to return the EGR valve to step 0 when 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

   Result

   Result	Proceed to
   Within standard range	A
   Outside standard range	B

B → See step   4 

A: Go to next step 

1. Check if the EGR valve are clogged with deposits.
2. Check if the EGR valve is closed.

   OK

   EGR valve is closed and no deposits.

   Result

   Result	Proceed to
   NG	A
   OK	B

B → See step   5 

A: Go to next step 

1. Replace EGR valve assembly. Refer to REMOVAL .

NEXT: Go to next step 

Fig 1: Identifying For Deposit (EGR Valve Assembly To Intake Ports)

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 the EGR valve assembly.
3. This check may require the removal of components.
4. Check if there is a build-up of deposits in the EGR valve or pipes.

   OK

   No deposits

NG → REPAIR OR REPLACE MALFUNCTIONING PARTS, COMPONENT AND AREA 

OK: Go to next step 

Fig 2: Exhaust Manifold Converter To EGR Valve Assembly

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 the EGR valve assembly.
3. This check may require the removal of components.
4. Check if there is a build-up of deposits in the EGR valve or pipes.

   OK

   No deposits

   HINT: 

   • This check may require the removal of components.
   • Check for blockage of the EGR valve assembly.

   OK

   No deposits

NG → REPAIR OR REPLACE MALFUNCTIONING PARTS, COMPONENT AND AREA 

OK: Go to next step 

1. Check for blockage of the EGR cooler assembly.

NG → REPLACE EGR COOLER ASSEMBLY 

OK: Go to next step 

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.
5. Read the MAP value.

   Standard

   Switch Condition	Techstream Display
   Power switch on (IG)	80 to 110 kPa (600 to 825 mmHg)

6. Put the engine in inspection mode. Refer to INSPECTION MODE PROCEDURE .
7. Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or more.
8. Enter the following menus: Powertrain / Engine and ECT / Data List / MAP.
9. Read the MAP value at idling the engine with the A/C switch and all accessory switches should be off and shift lever in P or N.

   Standard

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

   Result

   Result	Proceed to
   NG	A
   OK	B

B → See step   11 

A: Go to next step 

1. Check the intake system for vacuum leaks. Refer to ON-VEHICLE INSPECTION - Step 1 .

   OK

   No leaks in intake system.

NG → REPAIR OR REPLACE INTAKE SYSTEM 

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 power switch on (IG).
3. Turn the Techstream on.
4. Clear the DTC. Refer to DTC CHECK / CLEAR .
5. Turn the power switch off and wait for 30 seconds.
6. Turn the power switch on (IG) and turn the Techstream on.
7. Put the engine in inspection mode. Refer to INSPECTION MODE PROCEDURE .
8. 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 in P or N.

9. Drive the vehicle at 37 mph (60 km/h) for 5 minutes or more.
10. Idle the engine for 30 seconds or more.
11. Accelerate the vehicle at 37 mph (60 km/h)) then select the S4 range with the shift lever in S.
    WARNING:

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

12. 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.

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

    HINT: 

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

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

    HINT: 

    • If the judgment result shows ABNORMAL, the system has a malfunction.
    • If the DTC judgment result is INCOMPLETE or UNKNOWN and no pending DTC is output, accelerate the vehicle again at 37 mph (60 km/h) then select the S4 range with the shift lever in S, perform fuel cut operation for 5 seconds or more with the accelerator pedal fully released, and check the DTC judgment result.

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