Toyota LEXUS LS430 2005 Manual page 24

QUICK REFERENCE
NOTE:
Vehicles with the cruise control: When the cruise control is being used, even if you downshift from "D" or "6" (sixth range) to "5" (fifth
range), or "D" or "5" (fifth range) to "4" (fourth range), engine braking will not be enabled because the cruise control is not cancelled.
For vehicle speed reduction, see page 328. Vehicles with the dynamic radar/laser cruise control: When the cruise control is being
used in the conventional (fixed speed) cruise control mode or in the vehicle−to−vehicle distance control mode, even if you downshift
from "D" or "6" (sixth range) to "5" (fifth range) or D", or "5" (fifth range) to "4" (fourth range), engine braking will not be enabled because
the cruise control is not cancelled. For vehicle speed reduction, see pages 359 and 344.
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