Toyota Tundra Service Manual: Exhaust Gas Recirculation Flow Insufficient Detected (P0401)

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

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch ON and turn the Techstream on.
3. Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure) (See page ).
4. Turn the ignition switch off and wait for 30 seconds.
5. Turn the ignition switch ON and turn the Techstream on [A].
6. Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or more [B].

   HINT:

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

7. 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.

8. Idle the engine for 30 seconds or more [D].
9. Drive the vehicle at 60 km/h (37 mph) and select the S4 range with the shift lever in S [E].

   CAUTION:

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

10. 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.

11. Enter the following menus: Powertrain / Engine and ECT / Monitor / Current Monitor / Exhaust Gas Recirculation/VVT / Current [G].
12. Check that the Exhaust Gas Recirculation/VVT / Current monitor is Complete.

    HINT:

    If the monitor is Incomplete, perform the driving pattern again.

13. Enter the following menus: Powertrain / Engine and ECT / Monitor / Current Monitor / Exhaust Gas Recirculation/VVT / Details / EGR FLOW INSUFFICIENCY / Details.
14. Check the test Details (EGR FLOW INSUFFICIENCY).

    HINT:

    Make sure that the values are between MIN and MAX.

15. If the monitor is still Incomplete, perform the following procedure.
16. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
17. 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.
18. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
19. Input the DTC: P0401.
20. 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
    N/A	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 N/A and no pending DTC is output, drive the vehicle again at 60 km/h (37 mph) and 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 then check the DTC judgment result.
21. If the test result is INCOMPLETE or N/A and no pending DTC is output, perform a universal trip and check for permanent DTCs (See page ).

    HINT:

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

WIRING DIAGRAM

CAUTION / NOTICE / HINT

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.

  Data List	Change in Data List when Number of Steps is Increased Using Control the EGR Step Position Active Test
  Engine Speed	Idle becomes rough
  MAP	Pressure rises

• 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

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

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

(e) Read the DTCs.

HINT:

If any DTCs other than P0401 are output, perform troubleshooting for those DTCs first.

B

GO TO DTC CHART

A

(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 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:

NG

GO TO STEP 4

OK

(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.

OK

GO TO STEP 5

NG

(a) Replace the EGR valve assembly (See page ).

HINT:

Perform "Inspection After Repair" after replacing the EGR valve assembly (See page ).

NEXT

(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

(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

(a) Check for blockage in the EGR cooler assembly.

NG

REPAIR OR REPLACE EGR COOLER ASSEMBLY

OK

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

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

(e) Read the MAP value.

Standard:

(f) Read the MAP value when racing the engine.

Standard:

OK

GO TO STEP 11

NG

(a) Check the intake system for vacuum leaks (See page ).

OK:

No leaks in intake system.

HINT:

Perform "Inspection After Repair" after repairing or replacing the intake system (See page ).

NG

REPAIR OR REPLACE INTAKE SYSTEM

OK

(a) Replace the manifold absolute pressure sensor (See page ).

NEXT

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Clear the DTC (See page ).

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

(f) Turn the ignition switch to ON and turn the Techstream on.

(g) 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.

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

CAUTION:

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

(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.

NEXT

END