I have a 2005 BCGT.
The Bentley Assist Service manual says I have to remove the engine/transmission assembly to access the post cat o2 sensor on bank 2.
This seem ridiculous. Has anyone come up with a workaround for this problem?

would like to know this also

i heard that if u pull the motor you should re build your starter regardless if theres a problem or not because you have to pluck the the motor to do a starter.

we used to pull engines for o2 sensors but you can do all of them without puling engine. it is a struggle but can be done. also the starter motor is buried but rarely go bad.

Once we took off all the covers (engine/belly, etc.) we can see all the bolts for the pre-cat (top and bottom). We are assuming we'll have to take off the left half-shaft to get some access and free up the cat-back exhaust. Our thinking is to remove the pre-cat (which may be bad) and replace the pre-cat and both pre and post o2 sensors. Using this strategy, we feel 90% confident, we can do this without removing the engine/transmission. Do you think we are on the right track?

hello. we used to remove the subframe,with the an old engine crossmember we cut each corner so as we could use this as a support for engine,the engine then will have dropped about 1 inch,gives a little more access. if you do remove front axle you will get more turning room and ,i think we removed strut as well so your reach gets better.as this is your first one you will be doing it the best way you think best but you are going along the right lines.It can definitely be done.I will help you as much as i can over the internet .

Thanks for your insights. We'll continue to explore and research before going down the 'Rabbit Hole'. I'll keep you posted as the universe unfolds.

Sourced the parts from Scuderia Systems in the UK. Of note is that the nuts are Titanium and can only be used once. Yesterday, my local shop R&R the pre-cat and o2 sensors on bank 2. They have a lot of specialty tools and it took them seven hours to complete. However, given the alternative of removing the engine/transmission assembly (as recommended by the Bentley Assist service manual), this seems a very reasonable solution. Recognize that we had spent a lot of time ensuring we understood what was causing the error before we decided to do the job. When it was finished I asked the mechanic what he would do differently if he had to do it again and he replied "have smaller hands".

I have the Bentley factory diagnostic computer (VAS 5054) which is invaluable in chasing down problems. There were a number of seemingly insignificant issues including random misfires due to broken connections on the MAF sensors. In hindsight, this was far from insignificant. We did two independent smoke tests to ensure no vacuum leaks and we also replaced an exhaust manifold temperature sensor on bank 2. It is also of note that the old sensors were working correctly and the P0430 error was caused by a disintegrated cat. The final test is to put some miles on the car to ensure all is well.

those broken connections on the MAF,were they there before you did the o2 sensor ?

Subscribed.

Our guiding principle was to eliminate any and all errors (other than the P0430) before beginning the R&R on the cat. The broken connections on the MAF were present (and repaired with new connections) long before we tackled the cat. We also replaced the MAFs. Among other items we tackled prior to the R&R were plugs and ignition coils (just to be safe). We didn't want to put a new cat in without understanding what caused it to be dysfunctional in the first place. If we didn't do this, we'd blow the replacement cat. Computer testing of the o2 sensors suggested they were functioning properly prior to our undertaking. I was just hoping the sensors might be the problem so I could avoid the cost of the cat. Once we removed the exhaust behind the cat, chunks of debris fell out of the cat and knew we were correct in ordering a replacement at the same time as the o2 sensors. Anyone tackling this issue will quickly discover that replacing o2 sensors without replacing the cat doesn't make any sense due to the effort in getting the assembly out of the car.

Any reason , that you can see or figure out, for the cat failure. Are they metallic or ceramic....sounds like ceramic?
Is there a motor sport equivalent that can be used for longevity ?

We strongly suspect the misfires caused the failure. No vacuum leaks and the car ran perfectly with the failed cat. I replaced with the OEM cat which is ceramic (I believe). Don't know of any substitutions (although I looked). The collars at each end are unique to Bentley. Different than other w12 applications.

Thanks, I had read somewhere over here in the UK different cats can be bought . I will have to have another look and post if there is .

I am sure that Prindiville do 200 cell sports cats.

Les.

.....do you think the damage to Cat occurred while you owned the 2005GT or during prior owner...what mileage was on car when you repaired...what nuts were titanium...JimB San Francisco