Wow...do you have a stock air filter box, or an aftermarket cold air intake style air filter?

Its very difficult for water to get into the cylinders and not be burned off unless a gulp of water actually comes up to the level of the air intake.

You might be suspicious of a head gasket problem if the problem resumes.

Excellent thread.

I am having the same problem.. '99 GS300, 97K miles... CEL, VST and VST OFF lights all on, and completely in limp mode.
Before finding this thread, I already narrowed it down to the throttle position sensor, accelerator pedal position sensor or the throttle control motor. The challenge is to figure out which one it is, since none of them are cheap, and simply throwing parts at a problem (and hoping to hit it with the right one) is usually not the best way to solve it!
I did the continuity test outlined in the factory manual. Everything was within spec, except the throttle control motor was a tenth of an ohm over... but it was also much hotter than the 68F that the test was spec'd at.
I tried the other tests in the manual... turning the AC on at idle, and looking for the 50 rpm increase (it didn't) and turning the accelerator pedal position sensor (with the key on / engine off) while listening to the throttle control motor. The motor definitely responded to the inputs on the APP switch, but it also was making a continual high pitched buzzing, even when I wasn't turning the APP sensor.
I've never had the key on / engine off and operated the throttle.. with my head under the hood... so I don't know if this noise is normal.
It would be great if I had a known-good car to listen to, to compare, but I don't.

Does anybody know if this noise is normal... or could someone maybe give a listen to their own car and let me know what they hear (or don't?)

Thanks in advance!

When checking a component for OHMS, make "SURE" the temperature is equivilant to the OHMS. Reason why is, as temperature increases, resistance will change. So check the specs carefully.

Yes, I know that resistance rises with temperature, so a half ohm over spec is neither enough to be certain the part is faulty, nor can be even considered excessive, given the increased temperature in this instance. (Unfortunately there's not much way to run the tests at the specified 68F when the weather's in the 90s!)
That's a big part of why I'm curious about the noise from the throttle control motor. If they don't normally make that continuous buzz, that's a good indication that somethings wrong. (And if it is normal, I'll have to just keep looking!)

Thanks for your reply.

Hey checkers, I believe only Lexus techs have the specifications for the OHM the sensors should be reading.

I can however give you a few tips on what ive experienced, as well as what most others on this forum have experienced:

1) The TPS (Throttle Position Sensor) is usually NOT the problem, EVEN THOUGH Lexus and almost every tech will recommend you replace this first. Its the small sensor on the front right portion of the TB. All this sensor does is makes sure that the actual throttle plate valve is opening.

2) The Accelerator Positions Sensor is Most Likely the cause. Its harder to get to on the back side of the Throttle Body where the large diameter spring-loaded lever is where the throttle cable actually attaches to. There are 4 screws that hold it in, and requires that the entire TB be removed to access. This is the actual sensor that sends signal to the ECU, which sends a signal to the Throttle Controller Motor (also sometimes referred to as the Idle Control Motor) which actually opens the throttle disk butterfly valve.

3) The Throttle Controller Motor can also go bad. Virtually impossible to test. But easy to replace, if you can find one for sale. I found the part numbers at a few online parts stores a while back and posted them to this forum, youd have to go back and read older posts, maybe 2-3+ yrs ago.

The good news is, there are used TB's for sale via GreenLeaf or other outlets for less money than lexus will sell you the parts for, and its not a very difficult problem to fix.

Hope this helps a small amount.

Honestly, I don't know but he's works for the Service Dept of Lexus and pretty knowledgeable. I'm not going to doubt his work. It's been 2-3 weeks since that problem and no problem so far.

...just read the whole thread, sadly...mine turned on last night (CEL, VSC, VSC Off). i started the car just to move it up a little bit closer to the driveway from the sidewalk area. this blows...

Thanks for the reply, az-dave.

Looks like you're spot on, on it being the accelerator position sensor.
Going on a suggestion I read in another thread, I got a TIS cable and ran a scan. Two codes came up (and nothing else.) They were both for the accelerator position sensor.

Putting it in will be the easy part.. first I have to find a decent price on one.

For anyone else with the same problem, running a scan definitely eliminated the guesswork for me. I also ran the scan in generic OBD II mode, just to see what came up, and the same two codes came up (just without the descriptions.)
I was afraid that whatever code I found might include the whole system (TPS, accelerator position sensor, throttle control motor) but the codes were very specific.

What were the codes you pulled up? That would be awesome info for this thread and people who are sure to get this same problem.

Can u post a pick of what the lever assy throttle looks like

Ive never really heard it called a "Lever Assy Throttle" before.

I think they are referring to the spring-loaded part that the actual throttle cable connects to...

I wish I had a record of the numerical codes to post, but unfortunately I didn't make any notes before clearing the codes.
The good bit of info that I can offer is that using the TIS cable (and software) brought up trouble descriptions that were clear enough that I didn't need any other diagnostic information. (The $80, or whatever that cable cost, is probably the best spent money on a diagnostic tool I can think of, for anyone getting a CEL.)

BTW, "lever assy, throttle" is the part description in the Lexus/Toyota part system for the accelerator position sensor (part # 22060-46010 .)

Also, for anyone with a factory service manual, don't believe it when it says the throttle body has to be removed to replace the accelerator position sensor. With the right tools, a little patience, and maybe a mirror to get a clearer view of everything, the R&R can be done fairly quickly without removing any other parts. It does help to first remove the round lever (the part that looks like a little pulley) from the APS, to get better access to the locking tabs and the nuts that hold the APS on.

hey, my vsc and abs light came on after i lowered my car.

Search for a thread about the ABS sensor.

hey! new to the forum. Well, ive been driving the car around in limp mode for a while. CEL, VSC, ABS, VSC OFF lights on. Pulled a code P1125 and thats it. Replaced throttle motor, erased code, and same thing. Changed tps, and same thing. Car starts fine and everything but is really slow. Should I mention my ball joint fell off a while back. Fixed it and then the lights came on later. I have no idea what to do now. PLease help. Thanks