Trac Light On, Will Not Downshift

[MikeDubb]

I have a 1990 LS400 with 125,000 miles. I recently had the engine steam cleaned. Shortly after this, I notice that the Trac light would sometimes come on. Usually only on really hot days. Although the light would be on, I didn't notice any performance issues...until today I've always loved an opportunity to utilize the power of this great V8, so as I was going to pass someone on the freeway, I stomped on the gas pedal, and nothing happened . The car would not downshift. It started picking up speed, but very slowly because it would not downshift on its own. I manually downshifted, and it took off like normal. The Trac light was on. Later in the drive I noticed that the Trac light had finally turned off, so I stomped on the gas, and low and behold, it downshifted like it should and it took off. I called the dealership, who with all of their wisdom, told me that the Trac system must be malfuctioning (duh) and that I would have to pay them $95 for a diagnostic. (Does anyone know of a good Lexus mechanic in Seattle, Washington). I'm at a loss as this is an intermitten problem. I'm hoping that this is not a progressive problem. Any ideas?

[VBdenny]

Man, never steam clean an engine. What that does it spray steam, or hot water vapor, under very high pressure over all those sensors and electronics under the hood. The same parts Toyoto so very cafefully protected from water intrusion. Look under the hood of you LS after driving in the rain sometime, it is almost completely dry. Then go look under the hood of a Chevy and it is all wet with spray.

You probably had a vacuum line knocked off or broken by the pressure. You may also want to check all your vaccum lines as steam cleaning ages them rapidily. The most likely cause of the problem you are having is water in one or both of the distributor caps. Most problems are electrical in nature.

Sorry to go on and on, good luck with it.

[MikeDubb]

Thanks VBdenny,

I ran a diagnostic and am receiving a 41 error code. This is for a faulty throttle position sensor. I looked on lexls.com and found how to replace this item, but on the website it shows that there is only one TP sensor. My 90 ls has what looks like two??? I researched the web for the TP sensor and it does show that this part does effect the Trac system. I'm hoping by replacing this part, it will solve my problem. At this point, I am still confused though, as my throttle body has two identical sensors that look to be TP sensors and on lexls.com the picture only shows one. The part #'s on the two sensors are different, so when I get a chance, I'll give the dealership a call to find out the difference. If anyone has any additional info on Throttle Position sensors, please respond. Thanks for everyones help. I'll post a pic of my throttle body and the one from lexls.com tomorrow.

[SKperformance]

Don't the pics show 2 one for the throttle body and the other for the trac system?

[MikeDubb]

After more research, I found that one is the main throttle position sensor and the second is the sub throttle position sensor.