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lexpert, Lexus Master tech
Category: Lexus
Satisfied Customers: 9974
Experience:  Master Certified with lexus, 8 years experience with Lexus
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99 RX300: overdrive..warmed..2000 rpm until car gets..knock sensor

Customer Question

My '99 RX300 won't shift into overdrive once the car is totally warmed up. Also, occasionally (but infrequently# XXXXX will start off in overdrive #engine running around 2000 rpm until car gets up to 40+#. The only trouble code showing on the computer is related to the knock sensor. The car has about 180,000 miles. It has had recent engine work #including timing belt) and is running superbly.
Submitted: 6 years ago.
Category: Lexus
Expert:  lexpert replied 6 years ago.

Hello and thank you for using just answer!

Can you give me the exact code # XXXXX

Customer: replied 6 years ago.
I will have to get the code # XXXXX my mechanic here. I called and left a message. I'll send it as soon as I here from him.

For some clarification, the starting off in overdrive is a new symptom, since the last time the mechanic looked at the car. This morning, I left work to do some errands, and the car started off as usual (1st, 2nd, 3rd gear, but not into overdrive). Then at first stop light, car started off in overdrive, engine speed right up to 2000 rpm, until car was going 40+, then engine speed change with car speed, as normal. Car stayed in overdrive until next slow/stop, and continued to behave the same the next few times I started up (reverse functions normally all the time).
Then all of a sudden, operation reverted to the more normal of going through 1st, 2nd, and 3rd gears, but not into overdrive.
Again, I'll send the trouble code # XXXXX soon as I get it from the mechanic.
Expert:  lexpert replied 6 years ago.
Customer: replied 6 years ago.
I talked to the mechanic, and as best he can recall from records and memory (it's been 2+ months since he ran the diagnostics), the code was P0330. He apologized that his notation was not as clear as he'd like, and said if P0330 didn't "compute," it could have been P0335.

I hope this helps.

Harvey Knuth

Expert:  lexpert replied 6 years ago.
I'm sorry but if he did not properly notate the code then he is going to have to plug a scan tool into it and recheck it. We need to be sure that we are 100% sure on ALL and exact codes to be sure that I properly analyze and advise on this issue. Thank you.
Customer: replied 6 years ago.
I'll see what I can do. It'll at least be several week sometime.
Expert:  lexpert replied 6 years ago.
Customer: replied 6 years ago.
Good morning,
I finally was able to get my car back into the mechanic, and he confirmed the trouble code is P0330.
Also, although the issue of starting off in overdrive still happens, it is too infrequent to pin down anything directly related to it. However, I believe if the car is stopped and shifted into reverse, and then back into drive, the transmission returns to its current normal functioning...1st, 2nd, 3rd, but no overdrive (this has worked on at least two occasions).
Thank you,
Expert:  lexpert replied 6 years ago.
Ok thank you! You do indeed need new knock sensors then and the subharness thatconnects to them commonly falls apartwhen you change them so plan on replacing those as well.
lexpert and 3 other Lexus Specialists are ready to help you
Customer: replied 6 years ago.
OK, a follow-up question: I presume the need to replace the knock sensors is based primarily on the code P0330. However, is this in any way related to my transmission issue of not shifting properly (not going into overdrive once the engine is warmed up, or, occasionally, starting out in overdrive)?
Expert:  lexpert replied 6 years ago.
I outlined this already, the knock sensors cause the transmission issue, there is NOT a problem with the transmission. Get those sensors replaced.
Customer: replied 6 years ago.
Thank you for confirming that. However, I re-read all of your responses, and I can not find anything addressing the transmission issue. All I see is your request for the specific trouble code(s).
It would be helpful to have an explanation of how the (malfunctioning) knock sensors cause the transmission issue.
Thank you.
Expert:  lexpert replied 6 years ago.
sorry for delay. When a knock sensor malfunction is detected the computer goes into limp mode and causes the transmission to shift funny and to lockout overdrive, in other words it shuts down operation. Fix the knock sensors to fix that other issue as well Cool
Customer: replied 6 years ago.
Thanks very much.