riknchar

It turned out to be a simple Bank 2 O2 sensor that had gone bad, not the Hydrocarbon Switching Valve. It was repaired under warranty by Lexus (would have been ~$1k on my dime if I'd have had to pay).

I now have a 2010 LS600hL, and I'm hoping my Hydrocarbon device doesn't malfunction. But even if it does, there's no way I'd pay $7k to have it replaced (unless I could convince my warranty to cover it). There's no emissions check in Nebraska, and I don't think the switch really impacts the operation of the car itself, just reduces the emissions.

SpruceRain

SULEV is a US classification and has no impact here, but unfortunately we have mandatory yearly inspections in Finland for cars of this age, and a CEL would indeed fail the car.

I asked about this from a Lexus dealership here, and they said they'd never heard of this issue. They had a quick look at the thread and found the part numbers posted inconsistent with one Euro-spec LS600h that I'm considering. Apparently the picture of the exhaust part is different for the Euro cars, and these would seem to lack the places for the two valves. Not an official statement or completely certain either, but it is very encouraging for me.

stopdrpnro

Do you happen to have the write up for the work or the description of what they did from Lexus drivers? My bank 2 sensor 1 is causing a cel and they say you have to remove the engine and transmission. I was quoted $3800 just wondering if they replaced yours using a short cut. What dealership did the work??
Thanks

SpruceRain

Here are some EPC links and pictures:

US market LS600h exhaust

I'm guessing those longer cylindrical things are the hydrocarbon collectors, and those plunger valve -looking things are the notorious valves?

EU market LS600h exhaust

They're absent here.

Vansibel

You are correct the actuator is moving the valve by vacuum only, the car know if the valve opened by monitoring the exhaust gas temperature with the four temperature sensor. When the car start while the exhaust is cold a vacuum is applied to the actuator which close the valve and trap the cold exhaust gas into a chamber in the catalytic converter. There are 2 exhaust temperature sensor on each side that monitor the the temperature for the trapped gas and the other one the gas on the main chamber. In normal condition during this process the temperature of the gas should be different between the trapped gas (cold) and the gas in the main chamber (warmer), if it's not then the car knows that the valve have not closed properly and throw a code. In normal condition once the cold gas resulting from starting the car (which is a bit more polluting) gets warmer the car mix it in the main chamber by stopping the vacuum so the spring can mechanically reopen the valve to their open position. At least if the system fail the valve are usually stuck in the open position because of the spring so the car while throwing a CEL just function like a ls600hl from europe or japan where they don't have this feature in their exhaust system. A trick to pass emission that automatically fail with a CEL is to warm the car and the exhaust and then clear the code. It takes about three cycle of cold/warm start to meet all the condition again for the CEL. You can restart the car a dozen time in a row while the exhaust is hot and it won't change anything the code won't come back unless the exhaust cooled down, because if the exhaust is hot the valve won't need to be closed again. Also there is a "pending state" for the code occurring before the light appear giving you an additional cold start before the CEL light. Needless to say the car can be driven safely without any issue with the CEL as all it does is allowing the gas to just always mix like a regular ls460 of a japanese ls600hl. Obviously this is only in case the failure is with the valve and not the sensor which can sometime be the case. You can test if the closing mechanism is working properly before removing the exhaust by using a brake bleeder vacuum pump and apply a vacuum to the actuator lines. You'll hear the valve moving at around 20 inches Hg of vacuum if they are working properly.