CatK

I had my check engine light on and the traction control light come on not long after I got gas. I assumed I hadn't tightened the gas cap enough so I waited a few days. They were still on after a week. Took it to the dealership and they want $1,800 to fix those and the tire pressure sensor light that is on (which I had already been told was bad). Anyway, the day after I took it in, the check engine and traction lights went off. My question is would those go off without the service being done? If there is still something wrong with the car, those should stay on right? I'm just trying to figure out if I really need those services or if Lexus was just trying to make some money off me. Any thoughts, ideas, suggestions?

Clutchless

If the lights stay off, just keep driving. If they appear again go to a different Lexus dealer or a Toyota dealer or good independent shop as your Lexus dealer was ripping you off big time! That is far too much money.
You have not said what year or the mileage on your RX.
As they age (over 5 years) the tire pressure sensors in the tires wear out and or the batteries in them need to be replaced. Any tire store can take care of this for a lot less money! I bet that is your issue as opposed to some other expensive fix the dealer may have lied about.

tus

Would depend on what codes they pulled from the system.

salimshah

It is complicated.

You are doing the right thing by asking questions. First gen RX300 has a sticky 'Having problems, start here thread" and it covers lots of common issues and how to proceed. Instead of hashing them here, I would suggest visit that and get information about Check Engine Light.

Back to your experience with the dealer. For sure they are in the business of making money. They most likely hooked up the equipment and saw the actual codes and estimated the charge to fix and wanted to get your approval as they can not start work till you say that you are willing to pay the expected amount. If the shop then blindly goes ahead and replace the sensors they will get you. A good shop will do further investigation and check the parts to make sure they are actually bad. If they discover more stuff they will call to get approval for additional work/charge. If the part doesn't not need replacement, then they will fix their invoice and charge you less. This is the real test of honesty/integrity/competence. We all know that the labor rates at the Lexus dealership are high.

Salim