New guy here, got a 99 es300 that has 144k miles. Car doesn't shift into the last gear anymore and the rpm's stay high. For example, I can be going 50 and the rpm's will be at 3000 or so. CEL is on, took to autozone and got the code p0171, changed O2 sensors, cleaned the maf. I hear hissing under the hood, so I assume a vacuum leak is the reason for the code. The thing I'm scared of is I took my car to the mechanic and he told I would need a new transmission, wondering if any of you guys could help me out and tell me what exactly could be wrong with the car. Thanks!

 

I can't remember the code but when my car was acting like this it needed a knock sensor. I would disconnect the battery, reconnect it, and if would work again for a it.

 

Per chance , you don't have your overdrive button pressed on?

 

It's off as of now, have had it on and it doesn't make a difference at all. Gear still doesn't shift unfortunately

 

Is the Lexus in limp mode? I ask this because you say you still have an error code? If the problem is severe enough the car will go into limp mode to prevent damage to the engine caused by the problem.

First thing I would do is to fix the problem indicated by the error code (particularly if the car is in limp mode) and go from there. I know you don't want to put money into the car if you need a new transmission but if you don't believe your mechanic this would be the place to start.

One thing you could do, is clear the CEL and see if the car will shift before the CEL comes back on.

 

What does the transmission fluid like? What color is it? If it is not red you probably need to do at least one drain and refill. If you suspect the problem is transmission related try doing several drain and refills over a period of several weeks.

 

Thanks for the replies guys, so I went and got the vacuum leak fixed. Helped my gas mileage and car seems to have a little more power. Im gonna have my mechanic drain and fill the transmission fluid to see if that'll do the trick. Once again thanks to all of you

 

The car isn't in limp mode, did reset the CEL and car still wouldn't shift into the last gear. Hopefully the transmission fluid is the culprit!