Lexus 2004 GX470, Owner'S Manual

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MAINTENANCE
519
EMISSION INSPECTION AND
MAINTENANCE (I/M) PROGRAMS
Some states have vehicle emission inspection programs
which include OBD (On-Board Diagnostics) checks.
The OBD system monitors the operation of the emission
control system. When the OBD system determines that a
problem exists somewhere in the emission control system, the
malfunction indicator lamp comes on. In this case, your vehicle
may not pass the I/M test and need to be repaired. Contact
your Lexus dealer to service the vehicle.
Even if the malfunction indicator lamp does not come on, your
vehicle may not pass the I/M test as readiness codes have not
been set in the OBD system.
Readiness codes are automatically set during ordinary driving.
However, when the battery is disconnected or run down, the
codes are erased. Also, depending on your driving habits, the
codes may not be completely set.
Also, if the malfunction indicator lamp had come on recently
due to temporary malfunction such as a loose fuel tank cap,
your vehicle may not pass the I/M test.
The malfunction indicator lamp will go off after taking several
driving trips, but the error code in the OBD system will not be
cleared unless about 40 trips or more are taken.
If your vehicle does not pass the I/M test and the malfunction
indicator lamp does not come on, contact your Lexus dealer to
prepare the vehicle for re-testing.