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 lift amount of the EGR valve is controlled by a step motor operated by the ECM. The ECM operates the motor only a preprogrammed amount in response to the engine operating conditions (RPM, intake air volume to adjust the EGR volume to the target value.)
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 speed over 4,000 rpm
- Engine idling
- Park/neutral position switch ON





DETECTING CONDITION





WIRING DIAGRAM



SYSTEM CHECK DRIVING PATTERN
Purpose of the driving pattern
- To simulate DTC detecting condition after DTC is recorded.
- To check that the malfunction is corrected when the repair is completed confirming that DTC is no longer detected.





(1) Connect the OBDII scan tool or LEXUS hand-held tester to the DLC 3.
(2) Start and warm it up the engine with all accessories switched OFF
(3) Run the vehicle at 70 90 km/h (43 56 mph) for 3 minutes or more.
(4) Idle the engine for about 2 minutes.
(5) Stop at safe place and turn the ignition switch OFF.
(6) Start the engine and do steps (3) and (5) 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.
(a) The system check is incomplete.
(b) 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.

NOTICE: If the conditions in this test are not strictly followed, detection of the malfunction will not be possible.

INSPECTION PROCEDURE
LEXUS hand held tester













OBDII scan tool (excluding LEXUS hand-held tester)