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 and shift lever in P or N.

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 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 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 stalls
   MAP (Data List)	-	MAP value is at least +10 kPa (75 mmHg) higher than when EGR valve is fully closed

   HINT: 

   During Active Test, if the idling condition does not change in response to EGR step position, then there is probably a malfunction in the EGR valve.

NG → See step   4 

OK: 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 the EGR valve assembly. Refer to REMOVAL .

NEXT: Go to next step 

Fig 1: Identifying Intake Port 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 clogs in the pipes between the intake manifold and the EGR valve assembly.
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.

NG → REPAIR OR REPLACE MALFUNCTIONING PARTS, COMPONENT AND AREA 

OK: Go to next step 

Fig 2: Identifying Exhaust Manifold Sub-Assembly 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 clogs in the pipes between the exhaust manifold sub-assembly and the EGR valve assembly.
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.

NG → REPAIR OR REPLACE MALFUNCTIONING PARTS, COMPONENT AND AREA 

OK: Go to next step 

1. Check for blockage of the EGR with cooler pipe sub-assembly.

NG → REPAIR OR REPLACE EGR WITH COOLER PIPE SUB-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 when idling the engine with the A/C switch and all accessory switches should be off and shift position in P or N.

   Standard

   Engine Condition	Techstream Display
   Idling	Less than 80 kPa (600 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 .

   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 70°C (158°F) or more.

   HINT: 

   The A/C switch and all accessory switches should be off and shift position in P or N.

9. Drive the vehicle at 25 to 37 mph (40 to 60 km/h) with the shift lever in B.
   WARNING:

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

10. 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.

11. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes / Pending.
12. Read Pending DTC.

    HINT: 

    • If a pending DTC is output, the system is malfunctioning.
    • If a pending DTC is not output, perform the following procedure.
13. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
14. Input the DTC: P0401.
15. Check the DTC judgment 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

    HINT: 

    If the pending DTC is not output and the DTC judgment result is INCOMPLETE or UNKNOWN, drive the vehicle again at 25 to 37 mph (40 to 60 km/h) with the shift lever in B, 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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