principal

i have a yellow dash board light on my 2000 RX 300 and the manual says change the tail lights soon. i changed them all and the dash board lights comes back as soon as i step on the breaks. could this be a bad sensor, and if so where is the sensor? any help is appreciated.

code58

Mr P- when you changed the tail light bulbs did you change the 3rd brake light bulbs? (or is it bulb?) People often forget that bulb (or bulbs) When my DIL's came on (I only get the car occasionally to work on it and she seldom lets lights like that bother her so she doesn't call and mention it), I checked and at least 3 had filaments burned out. I went through them all and replaced all that were out (including 3rd brake light) and when I had my wife step on the pedal to test them, the dash light went out and after a couple times on the brake, they came back on and stayed on, even though ALL of them worked fine. Not knowing what to do, I gave her back the car, secure in the knowledge that they were all indeed working, though the dash light stayed on. I even checked ALL the other outside bulbs to make sure it wasn't one of them. ALL lights worked in ALL modes. I have read on a Lexus forum that they are kind off picky about the particular bulbs that you install (how often do you find a car "bulb out" light that is "picky"?) so I don't know if the draw that they sense is that precise that they know the difference between one brand of bulb and another. There are no Lexus bulbs, but there may be higher standards held in the Japanese bulbs than most of ours are build to (most are certainly not built here!) I don't know, but I doubt that it's a bad sensor, probably the lax standards the bulbs we have available are manufactured to.

principal

i have to agree that what you say makes perfect sense. Its very distracting to drive with this light and i would take out that DIL if i could... what is the third light bulb?

bob2200

I'd start with checking thec operation of the brake light that is at the top of the rear hatch (i.e., 3rd brake light). Then, I'd check the operation of all the lights (brake, stop, reverse, headlights, etc.). It is easiest to check them at night. The chances of it being a sensor are small. The wrong wattage bulb can trigger the warning light, but I don't recall hearing of different brands being a problem. I recently replaced a 21W bulb in a ES300 with (as I recall) a 22W bulb, and it worked fine.

sktn77a

iTrader: (2)

I don't believe there is any sensor, as such. The ECU monitors the current flowing through the various light circuits and flashes a warning light if anything is outside certain specifications. Your third brake light bulb is probably burned out but, failing that, you likely have a corroded light socket with a high resistance.

carguy07

Just had a thread on this. Mine is still intermittent and can't find any out.
https://www.clublexus.com/forums/rx-...emains-on.html

code58

Bob- in the other thread that carguy links to just above this post, someone refers to a sensor box in the lift gate, although he says 3rd generation, where my DIL's is 1st gen. ('99 RX). I am retired now but worked in automotive all my life and am very experienced in electrical. I am absolutely certain that I put the correct bulbs in and that ALL bulbs function perfectly normally in ALL modes. After I replaced the bulbs, I stepped on the brakes 2 or 3 times and the dash light went out the 1st time I stepped on the brake. It came back on about the 3rd time I stepped on the brake. I had my wife get in the car and go through all the operation of all modes and every bulb on the car worked perfectly, and now, approximately 5-6 mo. later they are still all working but the light has never gone out again. I have a ton of electrical testing equipment, but it's hard to get the car away from her and I don't know where to test except to look in the lift gate for a sensor box, especially since everything works fine and has continued to.

principal

Thanx guys for all the solid inputs on this topic. i am feeling a little dumb right now since i did not check the 3rd break light as yet. i will check it this evening and reply tmo..

sktn77a

iTrader: (2)

This is a nightmare in BMWs. If you get a bulb from your local Autozone, etc, you can almost guarantee you'll have a warning light go on. I hate paying the dealer $10 for a bulb that should cost less than $2!

principal

any one knows the code for that 3rd tail light bulb at auto zone?

carguy07

High mount stop light Part number = 921

https://www.clublexus.com/forums/388329-post3.html

code58

Thanks for the input Sktn. I am still suspicioning that is the case with some of the Lexus dash light indications of bulb out when there isn't a problem with the actual functioning of any of the lights. It is almost impossible to buy high quality bulbs at any of the chain auto parts stores. I remember years ago when I was working at a Chevy dealership (good one, not flakey), the parts manager bought a bunch of bulbs from a supplier that were made in some obscure foreign country. Bulbs looked really edgy right out of the box. About 3 out of 10 in the box wouldn't even light when you put them in. Even the MAJOR manufacturers (Sylvania, etc.) are not very high quality compared to good European or Japanese bulbs. It's all about the money.

principal

i will be leaving here soon to go home and try it, so lets hope that's the problem... to be continued tmo

principal

OK, its now official, I am dumber than I thought, or just aging. Now as i am changing the high mount stop light on my 2000 Lexus rx300 it suddenly hit me that i changed this very bulb 3 years ago when i just bought the darn car for the same light on the dash board. I am feeling so moronic right now for want of a more degrading word. And yes, just like 3 years ago it cleared the light again. Than you all for your well needed help.

code58

Glad it did the job Mr. P I guess I'll have to try different bulbs to see if my DIL's is not going out because of the bulbs. All lights are definitely working and correct # bulbs. Tough to ever get the car away from her though because they need both of the cars daily.