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

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

HINT: "INCMPL" is displayed when either condition (a) or (b) exists.
(a) System check is incomplete.
(b) There is a malfunction in the system.
- If there is a malfunction in 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 malfunction will not be possible.





WIRING DIAGRAM

INSPECTION PROCEDURE
LEXUS hand-held tester













INSPECTION PROCEDURE
OBD II scan tool (excluding LEXUS hand-held tester)