jsinton

Problem solved. I replaced the downstream O2 sensor with some OEM Denso ones. The original ones looked fine, but the resistance across the heat wires was a little low for spec. The new one resistance was 17 ohms, while the old ones were 14 ohms. It appears the P0420 and P0420 problem has gone away. But the VSC lights were still on, indicating the VSC system was disabled. I was unable to find information about that. Finally, my Dad took the car to the Toyota dealer. Apparently they knew this problem. They said the VSC system needed to be recalibrated. They calibrated it and problem is solved. So my theory is that somehow the O2 sensors being errant was able to corrupt the VSC system. I had disconnected the battery cable, but that didn't help. Only the dealer, apparently, could fix it.

I'm having the same problem with my Dad's 2002 ES 300: P0420 and P0430. It also has the TRAC and VSC lights on, which means there is a traction control failure. I pulled the O2 sensors out, they look fine. In any event, a P0420 code and a P0430 code both at the same time DOES NOT INDICATE A CLOGGED CAT! The P0420 means the front post cat O2 sensor has detected a reading fluctuation. The P0430 code is rear cat o2 sensor has detected a reading fluctuation. The chance of the same physical problem occuring at the same time to both front and rear is almost impossible. So there are other reasons why these codes might occur. They are: * Leaded fuel was used where unleaded was called for * An oxygen sensor is not reading (functioning) properly * The engine coolant temperature sensor is not working properly * Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe * Retarded spark timing * The oxygen sensors in front and behind the converter are reporting too similar of readings So my problem, along with the VSC light, is leading me to believe I have either an exhaust leak, a stretched timing belt, or the VSC is leaking. Probably the VSC, but I don't understand the damn thing yet.

I was afraid of that. Is there some instructions someplace I can view? My Hyundai is the same setup, and I thought that was a PITA.

Could someone please tell me where I can find the fuel filter in my 2002 ES 300? I looked around, but didn't find it. I got 66K and it's a little hard to start now, so I figure fuel filter is a good place to start. Thanks in advance.

how much transmission fluid does a 1996 ES300 hold? I really don't know, I just figure it holds about 3 quarts in the pan and 4 in the rest of the system. It's important not to overfill the system. I drain the pan and observe how much comes out. I try to change the trans fluid in the pan this way when I change the motor oil. It usually keeps the trans fluid in new condition.

If it's REALLY dark, i.e. it's clearly abnormally dark, then suspect that the radiator is leaking fluids between the radiator and the transmission. I had that happen in a 1996 Camry V6. The trans fluid kept turning almost black, and the coolant would also change a really dark color. I finally figured it out, and replaced the radiator.

Well, I pulled out the front bank of plugs, and you're right, they were like pristine. They were Denso Iridium plugs. Under the hood there is a sticker that says ONLY use iridium plugs, which I thought was interesting. So, I popped the old plugs back in... service done. Probably the plugs will outlast the rest of the car.

Thanks for the quick reply. I'll give it a go. When is the specified replacement interval anyway?

Hi there, I'm new to the forum and Lexus. My 2002 ES300 has 65,000 miles, so I figure it's time to change the plugs. Could somebody please point me to a post or a link to describe the little tricks I need to know to do that? Thanks in advance.