P0401
1UR-FE 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 stepper 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
CONFIRMATION DRIVING PATTERN
- Connect the Techstream to the DLC3.
- Turn the engine switch on (IG) and turn the Techstream on.
- Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure) DTC Check / Clear.
- Turn the engine switch off and wait for 30 seconds.
- Turn the engine switch on (IG) and turn the Techstream on [A].
- Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher [B].
HINT
The A/C switch and all accessory switches should be off and the shift lever should be in P or N.
- Drive the vehicle at 60 km/h (37 mph) for 5 minutes or more [C].
CAUTION:
When performing the confirmation driving pattern, obey all speed limits and traffic laws.
- Idle the engine for 30 seconds or more [D].
- Drive the vehicle at 60 km/h (37 mph) and shift the transmission to 2nd gear [E].
CAUTION:
When performing the confirmation driving pattern, obey all speed limits and traffic laws.
- Perform fuel cut operation for 5 seconds or more with the accelerator pedal fully released [F].
HINT
When "Idle Fuel Cut" in the Data List is ON, fuel cut is operating.
- Enter the following menus: Powertrain / Engine and ECT / Monitor / Current Monitor / Exhaust Gas Recirculation/VVT / Current [G].
- Check that the Exhaust Gas Recirculation/VVT / Current monitor is Complete.
HINT
If the monitor is Incomplete, perform the driving pattern again.
- Enter the following menus: Powertrain / Engine and ECT / Monitor / Current Monitor / Exhaust Gas Recirculation/VVT / Details / EGR FLOW INSUFFICIENCY / Details.
- Check the test Details (EGR FLOW INSUFFICIENCY).
HINT
Make sure that the values are between MIN and MAX.
- If the monitor is still Incomplete, perform the following procedure.
- Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
- 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.
- Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
- Input the DTC: P0401.
- Check the DTC judgment result.
HINT
- If the judgment result shows NORMAL, the system is normal.
- 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, drive the vehicle again at 60 km/h (37 mph) and shift the transmission to 2nd gear, perform fuel cut operation for 5 seconds or more with the accelerator pedal fully released, and then check the DTC judgment result.
- If the judgment result is INCOMPLETE or UNKNOWN and no pending DTC is output, perform a universal trip and check for permanent DTCs DTC Check / Clear.
HINT
- If a permanent DTC is output, the system is malfunctioning.
- If no permanent DTC is output, the system is normal.
WIRING DIAGRAM
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 values will change 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 FOR ANY OTHER DTCS OUTPUT (IN ADDITION TO P0401)
(a) Connect the Techstream to the DLC3.
(b) Turn the engine 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, perform troubleshooting for those DTCs first.
B -- GO TO DTC CHART SFI System
A -- Continue to next step.
2. PERFORM ACTIVE TEST USING TECHSTREAM (OPERATE EGR VALVE)
(a) Connect the Techstream to the DLC3.
(b) 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.
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the EGR Step Position.
(e) Confirm that Throttle Idle Position is ON and check the engine idling condition and the value of MAP 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:
NG -- REPLACE EGR VALVE ASSEMBLY
OK -- Continue to next step.
3. INSPECT EGR VALVE ASSEMBLY
(a) Confirm that there are no deposits on the EGR valve.
(b) Confirm that the EGR valve is closed.
OK:
There are no deposits and the valve is closed.
NG -- REPLACE EGR VALVE ASSEMBLY
OK -- CHECK FOR DEPOSIT (EGR VALVE ASSEMBLY TO INTAKE PORT)
4. REPLACE EGR VALVE ASSEMBLY
(a) Replace the EGR valve assembly Removal.
NEXT -- Continue to next step.
5. CHECK FOR DEPOSIT (EGR VALVE ASSEMBLY TO INTAKE PORT)
(a) Check for exhaust leaks at each connection point.
(b) 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.
(c) Check for blockage due to deposits in the EGR valve and pipes.
OK:
No deposits.
NG -- REPAIR OR REPLACE MALFUNCTIONING PARTS
OK -- Continue to next step.
6. CHECK FOR DEPOSIT (EXHAUST MANIFOLD CONVERTER TO EGR VALVE ASSEMBLY)
(a) Check for exhaust leaks at each connection point.
(b) 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.
(c) Check for blockage due to deposits in the EGR valve and pipes.
OK:
No deposits.
NG -- REPAIR OR REPLACE MALFUNCTIONING PARTS
OK -- Continue to next step.
7. INSPECT EGR COOLER ASSEMBLY
(a) Check for blockage in the EGR cooler assembly.
NG -- REPAIR OR REPLACE EGR COOLER ASSEMBLY Removal
OK -- Continue to next step.
8. READ VALUE USING TECHSTREAM (MANIFOLD ABSOLUTE PRESSURE SENSOR)
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG).
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / Data List / MAP.
(e) Read the MAP value.
Standard:
NG -- CHECK INTAKE SYSTEM
OK -- CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED
9. CHECK INTAKE SYSTEM
(a) Check the intake system for vacuum leaks Testing and Inspection.
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 engine switch on (IG).
(c) Turn the Techstream on.
(d) Clear the DTCs DTC Check / Clear.
(e) Turn the engine switch off and wait for 30 seconds.
(f) Turn the engine switch on (IG) and turn the Techstream on.
(g) 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.
(h) Drive the vehicle at 60 km/h (37 mph) for 5 minutes or more.
(i) Idle the engine for 30 seconds or more.
(j) Drive the vehicle at 60 km/h (37 mph).
CAUTION:
Strictly observe speed limits and traffic laws when performing the confirmation drive pattern.
(k) 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.
(l) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes / Pending.
(m) Read the pending DTCs.
(n) If a pending DTC is output, the system is malfunctioning.
HINT
If a pending DTC is not output, perform the following procedure.
(o) Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
(p) Input the DTC: P0401.
(q) Check the DTC judgment result.
Result
NEXT -- END