Join Date: Apr 2010
Ferrari Life Posts: 2,189
Aerguy, as Fabio has illustrated, your engine has 8 O2 sensors, however the OBD2 protocol maxes out at 4 (I think), so diagnosing a 12 cylinder Ferrari with 8 sensors using a generic OBD2 reader can be a challenge.
Where are you located, and is there any way you can get the car to a specialist who has a "real" Ferrari diagnostic computer, like an SD-2, SD-3, or even a Leonardo? One of these higher end computers should be able to tell you exactly which sensor is generating the problem.
Failing that, you're just guessing, and we're guessing too.
David (FluentinFerrari) may be able to shed some light on this as he has both the high end diagnostic computers as well as the generic OBD2's.
Edit: I found your posts on FChat and see that Motob (a very experienced and respected Ferrari tech) has given you great advice. You now know that the issue is either with the upstream or downstream sensor for cylinders 7/8/9. I think Motob was in error when he said cylinders 10/11/12. He was correct in saying the "rear manifold, left side" but he had the cylinder numbers incorrect.
Due to the difficulty of accessing the downstream sensor, I would probably opt to replace the upstream sensor and see if that cures the problem. Note: the upstream sensor is probably going to be a "wideband" O2 sensor, not a generic Lambda type, and hence it will be more expensive. Get the Ferrari P/N for it, and start searching on the internet for a generic Bosch replacement at a better price.
'99 550, Rosso Corsa / Nero, S/N:114654, Assy: 31836, Engine: 52084
High mileage, low compression, and missing on a few cylinders.....just like my cars.
Maranello Skunkworks Team Member
Last edited by cribbj; 08-05-2019 at 05:20 AM.
Reason: Updated Info