P0401

CIRCUIT DESCRIPTION
The EGR system recirculates exhaust gas, which is controlled to the proper quantity to suit the driving conditions, into the intake air mixture to slow down combustion, reduce the combustion temperature and reduce NOx emissions. The amount of EGR is regulated by the EGR vacuum modulator according to the engine load.
If even one of the following conditions is fulfilled, the VSV is turned ON by a signal from the ECM. This results in atmospheric air acting on the EGR valve, closing the EGR valve and shutting off the exhaust gas (EGR cut-off).
Under the following conditions, EGR is cut to maintain driveability.
- Before the engine is warmed up.
- During deceleration (throttle valve closed).
- Light engine load (amount of intake air very small).
- Engine racing.





DETECTING CONDITION





WIRING DIAGRAM

SYSTEM CHECK DRIVING PATTERN





(1) Connect the OBDII scan tool or LEXUS hand-held tester to the DLC3.
(2) Start the engine and warm it up with all accessories switched OFF.
(3) Run the vehicle at 70 ~ 90 km/h (43 ~ 56 mph) for 3 min. or more.
(4) Idle the engine for about 2 min.
(5) Stop at safe place and turn the ignition switch OFF.
(6) Start the engine and do steps (3) and (4) again.
(7) Check the "READINESS TESTS" mode on the OBDII scan tool or LEXUS hand-held tester.
If "COMPL" is displayed and the MIL does not light up, the system is normal.
If "INCMPL" is displayed and the MIL does not light up, run the vehicle again and check it.

HINT: "INCMPL" is displayed when either condition (a) or (b) exists.
- The system check is incomplete.
- There is a malfunction in the system.
- If there is a malfunction in the system, the MIL will light up after steps (2) to (6) above are done.

INSPECTION PROCEDURE

LEXUS hand-held tester




























OBDII scan tool (excluding LEXUS hand held tester)