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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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1999 Lexus RX300 awd transmission wont shift into overdrive

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1999 Lexus RX300 awd transmission won't shift into overdrive when engine is warm (after 10-20 miles)
Hello and thank you for using just answer.
Do you have any chek engine lights coming on?
How many miles are on the truck?
Did you just purcahse the vehicle?
Once it reaches normal operating temperature this issues is gone corret?
Customer: replied 8 years ago.


The check engine light is on with a lean condition code. Vehicle has 150,000. Transmission serviced at Lexus dealer at 100,000 fluids and filter changed. Fluid was dirty. Today fluid is again dirty. I have owned vehicle since new, driven lightly. At operating temp is when problen occurs. Transmission shifts normally when cold then refuses to upshift to overdrive after 10-20 miles. It has been doing this for 4 days and about 300 miles. I am going to flush the fluid and change the filter tomorrow hoping this will help. My mechanic things there may be wear in the transmission causing the malfunction

Thank you for the reply.
I would get the codes scanned again!
No changing the fluid will most likely NOT alter this condition.
The reason I comment on codes is that there are a few issues/codes that will actually lock out overdrive as a failsafe mode.
As you are already aware you know that the transmission locks out overdrive when COLD but if this is a HOT condition then this is a actual issue.
Get me current code #'s.
Customer: replied 8 years ago.
I wrote down the codes, but don't have them with me. The mechanic at the shop looked them up and found lean burn condition. There were 8 possibilities we found, but his reader was not sophisticated to go any further. There were no '700 ?' codes for transmission malfunction.
I understand that but a mechanic that does not specialize in Toyota/Lexus giving his interpertation of the codes is of no help here. I am highly factory trained on this vehicle, if you can reply bak to me with the code #'s I can better analyze this myself.
Customer: replied 8 years ago.
How can I get back in touch with you? The codes are not at my computer site, can I phone?
No phone or personal contact allowed by site rules, just log back in here and reply when you can. I am online every evening. You should have a bunch of e-mails by now that can link you back here.
Customer: replied 8 years ago.

Hi Peter


The codes are P0171, P0330.

Ok so you have 2 issues here:
1- the 171 code is for lean, you need to have the mass air flow sensor cleaned out, most likely it will need to be REPLACED but clean it first try cleaning to try to save some $$$$, this is the little sensor on the top of the air filter box held in by 2 screws and has 5 wires running to it.
2- The P0330 code is for knock sensors. Check the engine wiring harness for any signs of rodents chewing on wires, no problem found here then you need to have BOTH the knock sensors replaced and the little sub-wiring harness replaced, this is a EXPENSIVE repair as the intakes both have to be removed and parts are about $400.

The service manual does show P0330 to trigger fail safe mode which can lock out over drive.....
lexpert and 2 other Lexus Specialists are ready to help you
Customer: replied 8 years ago.

Hi Peter,

Thank you for the code reading and advise. I cleaned the mass air flow sensor and the 0171 code cleared. I flushed and changed the transmission fluid (it was due for service) and the transmission still fails to upshift into overdrive after 10 minutes of driving (when engine is cold overdrive locks out, then for a few minutes overdrive is available and stays locked in until car slows and shifts down, from then on no overdrive). Now the code P0330 returns and indicates knock sensor 2 is the fault. Do I need to change both knock sensors or is it safe to change just #2 on the front cylinder bank? The time estimate is 3.3 hrs for the change so doing both would make sense except that the sensors are $216 each from the dealer. I found knock sensors on the internet mailorder for $157.02 each, is it safe to uses aftermarket parts for this? Is there a specific parts number for the 1999 model? Is the harness a separate part? Do I need anything else besides the manifold gasket for the reassembley? Thanks for the great advise.

Thank you for the reply and follow up, I figured cleaning the sensor would clear that code and resolve the issue (as well as save you from paying for a new sensor!)


We already touched on the knock sensor issue previously, as I stated if there is no signs of rodent damage to the harness then proceed as I recommended. YES these sensors are VERY expensive but you do NOT want to pay another 3.3 hours labor to go back in there if the other one fails. No do not use aftermarket parts, if you are looking for a wholesale price on OEM factory toyota parts then go to and order BOTH sensors as well as the sub wiring harness for these sensors (it will crumble when removed from the old sensors).

Let me know if you have any follow up questions, thanks.

Customer: replied 8 years ago.

Peter, has knock sensor part # XXXXX for engine 1MZ-FE Sienna which appears to be equivalent to the lexus pasrt number 89612040 called for on RX 300 1MZ-FE on Alldata, Are they interchangeable, identical? Metro did not offer the Lexus part.

Thank you, Will

The computer locked/filtered out the part# XXXXX tried to list, ALLDATA is very unreliable for part #'s as they supercede often, the engine in your RX is identical to the 2003-2004 Avalon engine, I know for a fact that you can get the parts from toyota as I have done this myself on late model RX vehicles, call your Lexus parts department and request the part # XXXXX price for the sensor and sub wiring harness (pretend you intend to purchase and they are always willing to give you this), then use these current part #'s on the site, thanks