rbackous

I'm new to this forum, so thanks in advance to anyone that can help!

My car doesn't seem to want to shift into the final gear on warm days, after the car has been running for maybe 15+ minutes. When it has happened to me, turning off the car and restarting it (like at a red light) has ALWAYS worked for me. My son has been driving the car lately and he says that's not working for him. But he seems to think it's tied to having the air conditioner running. If he turns off the air, it'll shift for him again.

I've had my car in the shop several times for this problem. They said the codes indicated bad knock sensors and changed them, 1st one bank and then the other. That didn't fix anything and cost me dearly. Then it seemed the alternator was going bad. I replaced that last weekend and my son had the problem again driving home.

Can anyone suggest something else to try?

Thanks!

msekanha

Is the check engine light still on?

tomf

^ on the CEL. A pending error could also cause this. Depending on the error ECM does not let the car shift to overdrive. Also if you have a Knock sensor error the ECM could possibly put the car in limp mode.

rbackous

The check engine light does come on from time to time. Sometimes it goes off after turning off the car and other times it'll stay on for a few days. But it doesn't always equate to the car not shifting. In other words, it might still shift with the light on or it might not shift even though the light is not on.

tomf

Also the ES300 will not shift into overdrive until it is warmed up, usually about 5 minutes or so. A pending error will not necessarily light the CEL but could prevent shifting into overdrive. What is the error code associated with your CEL?

hypervish

Was the replacement knock sensor OEM?

rbackous

No. I was informed of this after the fact.

rbackous

Sorry I don't know the exact code. All I know is my mechanic told me the code indicated it was the knock sensors. I have experienced what you mentioned about the car needing to warm up (I'm in Minnesota), but it's not the case here. This seems to be the opposite of that.

PFB

As Tomf mentioned, Inside the transmision there is a temperature sensor that prevents the transmission from engaging into overdrive until the transmission fluid warms up.

I believe that the knock sensor code, and the A/C being off fixes the shifting problem, is nt related, and is confusing you.

If that temperature sensor is defective, or if it misbehaves when the temperature is warm, it could potentially think that the transmission fluid is still cold, and prevent it from shifting.

I don't know what it's resistance measurements are supposed to be at various temperatures, so maybe someone else could chime in. There could be other possible causes, such as bad wiring, bad connections, defective solenoid, defective transmission management computer, etc.. Your starting point however should be to verify that transmission temperature sensor.

A Lexus dealer with his more sophisticated and specialized diagnostic tools could diagnose the functionlity of that sensor through the OBD II port. Infact, that's probably your best bet. He is also equipped to retrieve trouble codes, that a normal OBD II diagnostic tool can not retrieve.

All you need him for is the diagnosis. You can than have the work done elsewhere.

Phil

hypervish

That could be the issue. Aftermarket sensors do not play well with these cars.

Take it to autozone next time the CEL pops up, and they will check it for free. Post the code here.

Mphidd

In plain English can anyone provide any info on this? I'm having the same issue with my 1999 ES300 and just had the knock sensors, water hose, gaskets, and wiring harnes replaced by my mechanic. I did not inform him of the car not shifting because my partner drove th car and said it was fine. I drive the car again today after having the work done and I know for a fact it doesn't shift to 4th gear.

The check engine light is not on but I feel like the car isn't shifting correctly.

RXGS

iTrader: (2)

My car had the same issues and it was the knock sensor, replaced it with a toyota one as I was told aftermarket ones have issues. I know that there are two of them, so maybe one of them or wrong installation could be the reason

lostape45

Mine was caused by a bad oil control valve. But the knock sensor is more likely since you just got them replaced. Like 02SDGS said above, they almost have to be OEM knock sensors to work properly.

Mphidd

Would it throw any type of error code?

lostape45

Usually knock sensors do. I've heard of oil control valves not throwing codes though. In this case you wish you had a check engine code so you could pinpoint the problem.

Did you have the knock sensors replaced with toyota ones or aftermarket ones?