P0401

2ZR-FXE ENGINE CONTROL: SFI SYSTEM: P0401: Exhaust Gas Recirculation Flow Insufficient Detected
P0401 - Exhaust Gas Recirculation Flow Insufficient Detected

DESCRIPTION

Based on the driving conditions, the ECM regulates the volume of exhaust gas that is recirculated to the engine's combustion chambers and thus lowers the combustion temperature to reduce NOx emissions. The ECM monitors signals such as engine speed, coolant temperature, electric load, and vehicle speed. When the EGR permission conditions are fulfilled, the ECM controls the opening of the EGR valve linearly through signals to the EGR step motor.





MONITOR DESCRIPTION

The ECM monitors the pressure inside the intake manifold while opening and closing the EGR valve during fuel cut operation. If there is no change in the manifold absolute pressure sensor value, the ECM interprets this as a malfunction in the EGR valve assembly, illuminates the MIL and stores the DTC (2 trip detection logic).

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS





TYPICAL MALFUNCTION THRESHOLDS





MONITOR RESULT

Refer to detailed information in Checking Monitor Status Mode 6 Data.

P0401: Exhaust Gas Recirculation / VVT / EGR FLOW INSUFFICIENCY





CONFIRMATION DRIVING PATTERN





1. Connect the Techstream to the DLC3.

2. Turn the power switch on (IG) and turn the Techstream on.

3. Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure) Reading and Clearing Diagnostic Trouble Codes.

4. Turn the power switch off and wait for at least 30 seconds.

5. Turn the power switch on (IG) and turn the Techstream on.

6. Put the engine in inspection mode (maintenance mode) Component Tests and General Diagnostics.

7. Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher [A].

8. Accelerate the vehicle to 60 km/h (37 mph) or more by depressing the accelerator pedal for at least 10 seconds [B].

CAUTION:
When performing the confirmation driving pattern, obey all speed limits and traffic laws.

HINT
When accelerating the vehicle, depress the accelerator pedal more than normal to start the engine.

9. Idle the engine for 30 seconds or more [C].

10. Accelerate the vehicle to 60 km/h (37 mph) with the shift lever in B [D].

CAUTION:
When performing the confirmation driving pattern, obey all speed limits and traffic laws.

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

HINT
When fuel cut is operating "Idle Fuel Cut" in Data List is ON.

12. Enter the following menus: Powertrain / Engine and ECT / Monitor / Current Monitor [F].

13. Check that Exhaust Gas Recirculation / VVT / Current is Complete.

HINT
If the monitor item Exhaust Gas Recirculation / VVT / Current is Incomplete, perform the driving pattern again.

14. Enter the following menus: Powertrain / Engine and ECT / Monitor / Current Monitor / Exhaust Gas Recirculation / VVT / Details.

15. Check the Details (EGR FLOW INSUFFICIENCY).

HINT
Make sure that the value is between MIN and MAX.

16. If the monitor item Exhaust Gas Recirculation / VVT / Current is still Incomplete, perform the following procedure.

17. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

18. Read the pending DTCs.

HINT
- If a pending DTC is output, the system is malfunctioning.
- If a pending DTC is not output, perform the following procedure.

19. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

20. Input the DTC: P0401.

21. Check the DTC judgment result.





HINT
- If the judgment result shows ABNORMAL, the system has a malfunction.
- If the judgment result shows NORMAL, the system is normal.
- If the DTC judgment result is INCOMPLETE or N/A, perform steps [D] and [E] again.

22. If the judgment result is INCOMPLETE or N/A and no pending DTC is output, perform a universal trip and check for permanent DTCs Reading and Clearing Diagnostic Trouble Codes.

HINT
- If a permanent DTC is output, the system is malfunctioning.
- If no permanent DTC is output, the system is normal.

INSPECTION PROCEDURE

HINT
- By using the Control the EGR Step Position Active Test, the operation of the EGR valve can be checked.
- When the engine is idling steadily with the EGR valve fully closed, if the EGR valve is normal and it is opened using the Active Test, the Data List value changes as follows.






- Read freeze frame data using the Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air fuel ratio was lean or rich, and other data from the time the malfunction occurred.

PROCEDURE

1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0401)

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

(e) Read the DTCs.

Result





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

B -- GO TO DTC CHART SFI System
A -- Continue to next step.

2. PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE EGR STEP POSITION)

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Put the engine in inspection mode (maintenance mode) Component Tests and General Diagnostics.

(e) 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 and shift lever in P or N.

(f) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the EGR Step Position / Data List / Primary / MAP.

(g) 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.

Standard:





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 -- REPLACE EGR VALVE ASSEMBLY
OK -- Continue to next step.

3. INSPECT EGR VALVE ASSEMBLY

(a) Check if the EGR valve are clogged with deposits.

(b) Check if the EGR valve is closed.

OK:

EGR valve is closed and no deposits.

Result





B -- CHECK FOR DEPOSIT (INTAKE PORT TO EGR VALVE ASSEMBLY)
A -- Continue to next step.

4. REPLACE EGR VALVE ASSEMBLY

(a) Replace the EGR valve assembly Removal.

NEXT -- Continue to next step.

5. CHECK FOR DEPOSIT (INTAKE PORT TO EGR VALVE ASSEMBLY)





(a) Check for exhaust leaks at each connection point.

(b) Check for cracks, damage, and clogs in the pipes between the intake manifold and the EGR valve assembly.

(c) This check may require the removal of components.

(d) 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 -- Continue to next step.

6. CHECK FOR DEPOSIT (EXHAUST MANIFOLD SUB-ASSEMBLY TO EGR VALVE ASSEMBLY)





(a) Check for exhaust leaks at each connection point.

(b) Check for cracks, damage, and clogs in the pipes between the exhaust manifold sub-assembly and the EGR valve assembly.

(c) This check may require the removal of components.

(d) 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 -- Continue to next step.

7. INSPECT EGR WITH COOLER PIPE SUB-ASSEMBLY

(a) Check for blockage of the EGR with cooler pipe sub-assembly.

NG -- REPLACE EGR WITH COOLER PIPE SUB-ASSEMBLY
OK -- Continue to next step.

8. READ VALUE USING TECHSTREAM (MAP)

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine and ECT / Data List / Primary / MAP.

(e) Read the MAP value.

Standard:





(f) Put the engine in inspection mode (maintenance mode) Component Tests and General Diagnostics.

(g) Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher.

(h) Enter the following menus: Powertrain / Engine and ECT / Data List / Primary / MAP.

(i) Read the MAP value when idling the engine with the A/C switch and all accessory switches should be off and shift lever in P or N.

Standard:





Result





B -- CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED
A -- Continue to next step.

9. CHECK INTAKE SYSTEM

(a) Check the intake system for vacuum leaks Intake System.

OK:

No leaks in intake system.

NG -- REPAIR OR REPLACE INTAKE SYSTEM
OK -- Continue to next step.

10. REPLACE MANIFOLD ABSOLUTE PRESSURE SENSOR

(a) Replace the manifold absolute pressure sensor Removal.

NEXT -- Continue to next step.

11. CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Clear the DTCs Reading and Clearing Diagnostic Trouble Codes.

(e) Turn the power switch off and wait for 30 seconds.

(f) Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.

(g) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes / Pending.

(h) Read the pending DTCs.

HINT
- If the pending DTC is output, the system is malfunctioning.
- If a pending DTC is not output, perform the following procedure.

(i) Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

(j) Input the DTC: P0401.

(k) Check the DTC judgment result.





NEXT -- END