99 Gs300 Shifting Problem

[coachmac]

My 99 GS300 recently does not shift to certain gears. It will shift in gears 1-4, but will under no circumstance go to 5th gear. It also does not downshift when I accelerate from the 60 mph mark and above. And, it will not shift from a higher gear to a lower (like if you would make a turn then slam on the throttle, or if you were at a halt and slammed the throttle, the car will just accelarate at a sluggish bog). Is it possible that this is a ECU problem or a strictly transmission problem?

[GuyTelefunken]

Humm.. Interesting questions.

First, I would disconnect the negative battery cable for a few minutes to let all the adaptive memories reset. Lexii love to learn the habits of their driver and environment.

Next, as obvious as this may seem, make sure the gear selected is "D" not 4 and the the ECT mode switch is set to Normal or Power but not Snow. Though, the transmission will be a little reluctant to shift in Snow mode, it should still kick-down when you put your foot to it.

If none of this helps the situation, I would advise a trip to the dealer to look for codes; specifically in the transmission control module. The codes found here are not usually available to mechanics without either specialty transmission software or a Lexus computer.

If there is a transmission problem, there is a high likelyhood of codes being set in the TCM.