After doing the transmission swap on my 98 SC300 from the old one dying and putting the exhaust and driveline back together, a few days later I got a P0430, P0441, and P0446 after just a day or two of driving. Having them scanned revealed they were cat and evap system related. I thought it was just too coincidental that they always ran fine before taking all that apart for them to randomly foul out a day or two later.

My friend that helped me with the job is a very competent mechanic, and Lexus, specifically an SC, enthusiast. Usually he can tell me exactly what the problem is just by a description and is always dead on.

I drove the car that way until I was able to get it to his house today, and within 6 seconds, maybe even less, he showed me exactly what it was. Maybe this can help you guys or someone in the future who may be searching for a solution to this problem before they spend a bunch of money that isn't needed.



If you look closely, at the bottom of the throttle cable bracket, you can see a plastic nipple with no hose on it. If you look closely, just above the purple pcv valve, you can see a hose that is just lying there. Do the math...

He told me that after sitting for a few days sometimes, the gas pressure in the tank can pop that vacuum hose off of that valve and cause those codes. He said it does it after sitting for a day or two sometimes on his GS430. My car sat for a couple of months.

Anyways, not saying that is going to be the cure for everyone that will have this problem, but it was the cause of mine, and he said it's quite common. It's a free check in case your car is throwing that code that may save you a bunch of money, buying parts that aren't the problem.