Speed Sensor?

[bluestu]

I've been having a problem for the past four months with my RX300 not shifting properly after the car is warmed up and restarted. It will miss shifting into second gear just one time at low speed and the check engine light will come on and go back off after about the third or fourth startup. The car will shift fine for several days and then do the same thing again. I took it to the shop and they said it was the speed sensor and replaced it. It did not remedy the problem. I took it back and they said everything checked out including the transmission and they didn't know what the problem was. I was wondering if it might be a computer problem or maybe another bad sensor??? Sometimes the car will go for as long as a week before messing up. I even took it on a long trip and had no problems at all. There are no strange or unusual noises either. I'm sort of stumped on this one. I've had quite a few sensor problems with this car and I'm becoming very annoyed with this one. Does anyone have any ideas as to what might be causing this problem and what I should do about it??? thanks.

[RX in NC]

Sure hope that you are not experiencing early warning signs of impending transmission failure....

I wonder if in doing all of that transmission flushing you endorse, you've now dredged up significant amounts of particulate matter that had settled into the transmission pan (and would have been easily removed through normal drain-and-fills) but is now lodged throughout your transmission valve bodies and is beginning to interfere with shifting performance?

I'm sure that your tranny shop will say no since they certainly want to avoid the liability, but it may now behoove you to spend some time researching this possibility....

[lenore]

Maybe the temperature sensor is faulty, the one that does not allow the transmission to shift into overdrive until warm....Only other thing is to unhook the battery for 30 minutes and reconnect and see if the ECU will relearn....other than that I agree with RX that it may be a tranny time....sorry my friend good luck... Another thought, unhook the electrical connector to the transmission and reconnect, maybe the contacts are corroded....

[bluestu]

I thought I might hear from you guys. Since I'm the poster boy for transmission flushes, maybe you guys are right. If it is the transmission, it hasn't gotten any worse since it started missing four months ago. There are no strange noises and it does it very infrequently and randomly. I've owned several cars that had transmissions go out, so I'm well aware of what happens when the transmission starts to fail. The symptoms are continuous and get progressively worse with time. Believe me, I'll be the first to post when my transmission does fail.

I've already tried resetting the computer. The shop I took it to pulled the pan and said everything looked normal. They have a high-end diagnostic machine and said the code read speed sensor. I'm thinking it could be a wiring, sensor, or computer problem since the symptoms haven't changed or worsened. Where is the wire located that goes to the transmission??? There is a very good transmission shop down the road from my house. They're very honest and reputable. Do you think I should have them check it out???

How many miles on average should an AWD RX300 transmission last??? That's a topic that I haven't seen discussed yet.

[RX in NC]

If it were my vehicle and the shifting problems remained very infrequent and intermittent, I would not do anything to the vehicle at this point other than to drive it normally and pay very close attention to the shift patterns in an effort to determine if they were worsening. Of course, I wouldn't plan any long trips away from home in this particular vehicle, either. But I would start doing the research on the problem in an effort to better understand what is taking place. Talk with the tranny shop guys that you trust, and not just one shop - get multiple opinions. Let them drive the vehicle and if they offer free analysis with their diagnostic equipment, by all means do it. But I wouldn't blindly start swapping parts until I had a much better understanding of what was going on. You need to wait until your symptoms worsen and become predictably consistent before you start spending money on what may or may not turn out to be a potential fix. Without a consistently accurate diagnosis (probably from at least two different sources) you're just guessing, and for something as expensive as a potential transmission rebuild, I would want to have all questions answered before I opened my wallet.

As far as how long an AWD RX300 transmission should last, your experience on this site over the years should tell you that the answers could be all over the map. Ours showed early signs of failure at 48,000 miles even though the fluid was changed at 30,000 miles even when the owners manual clearly states "no need to change it". Lexus replaced our transmission, and my wife drove the vehicle another 81,000 miles before we sold it to a third party back in January. I did drain-and-fills every 30,000 miles and advised our buyer to keep this process up without fail. Others on this site seem to forget all about transmission fluid maintenance and manage to obtain 100,000 miles or more with no problems. So who really knows what a typical RX300 AWD transmission lifespan is....