Transmission shifts into overdrive once but when slowed to a stop or near stop will not shift into overdrive again unless shut-off and re-started. Overdrive switch is OK and activated.
SOURCE: transmission won't go into overdrive when engine is hot
Lexus's have a complicated system of electronics that control the function of the transmission.Under normal operating conditions the transmission is controlled by the ecu and by a secondary system called a drivetrain control module. usually when a fault occurs it sends a code to the ecu and the check engine light comes on.
If this light does not come on then typically the electronic modulator is at fault and needs to be replaced.
If the check engine light comes on when the vehicle is hot i need this code to guide u further for the repair.
If u want to attempt the repair , be wary. its messy and takes time to do to do it right.
SOURCE: not shifting into overdrive and check engine light
I'm not a lexus guy , but I'm thinking that you have a vacuum leak somewhere.
SOURCE: 1999 Lexus RX300. Does
A knock sensor code has nothing to do with OD engagement, most likely the OD solenoid is sticking or the OD is magnetic clutch is defective inside the transmission torque converter, any Trans shop will road test and give u a preliminary diagnosis for free, suggest you do that.
SOURCE: rx300 with 143000 miles, overdrive won't engage
Start by checking the least expensive items: Make sure you are not activating the O/D switch in the shift stick inadvertently. Look at the display panel, if the "Eng" light is on, you must get the code and repair the affected item. If you have knock sensors and/or oxygen sensors malfunctions that may prevent the transmission from shifting to O/D. Check the ground cables located in the engine compartment, especially the ones behind the air intake manifold. If they are loose or broken it affects the ECU (car computer) and causes the transmission to work erratically. If they become disconnected it may burn the ECU and shut down the car. Now going to more profound mechanics, it could be a sticking shift solenoid valve, your RX300 transmission have five of those located were the transmission oil strainer (filter) is. It can also be an ECU malfunction and/or related to the wiring from the ECU to the transmission connectors. Always start from the least expensive and recheck the obvious. Good luck.
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