456M GTA Slow Down light

Considering that OEM cat CUs are a known weakness that always end up failing sooner than later I see little point in attempting to diagnose "slow down" issues before investing in Technistrada's bulletproof replacements. These, an upgraded fuseboard and an external cooling harness are the "big 3" must-haves for our cars.

 

None of which I have ever felt compelled to install in any clients car to keep it reliable.
Gotta love internet diagnostics.

 

Lol... Earth is flat too.

 

I had a slow down light in September after my 1995 456 GT had been sitting at the shop for about a year and a half. When it was started and run for the first time, the slow down light appeared. I then asked the shop to perform a timing belt service, and the slow down light went away.
I'm not sure if this is the issue with your car if the catalytic converters are not heating up. I also have the Technistrada units, and they work well, even though my 456 is before vehicle assembly number 17495 (as noted on Technistrada's website).

Good luck!

 

On my 550 the slow down message only blinked eratically at idle and urban speeds, disappearing above 30 mph, suggesting to me that the ailing OEM cat CUs (updated green units) were suffering from the heat in the engine bay, and that was with a car that came decatted, meaning less heat in the engine bay. The slow down message completely went away after fitting Technistrada's cat CUs. The manual suggests that the slow down message has to stay on permanently to register a proper malfunction, which I suppose would cause the ECUs to switch into limp mode, but that has not been the case on my 550. As the car came decatted I suppose the ECUs were retuned to at least disable any error message triggered by the deleting of cats, as suggested by F. Fiammenghi when I visited him to purchase race headers, and some people have used more or less successfully "O2 spacers" on the secondary lambda sensors to mimic the presence of cats when they have been deleted.

I can well understand the desire to drive the car after spending much resource in it - BTDT with wrenching on it perhaps like 50 hours after purchasing it before I knew it was ironed out. It has since run like swiss clockwork with zero error message or issues, and I have racked up ~15000 km in 3 years. It runs so well that it seems to thank me for sorting it out and using it as much as it needs. Such a piece of mind with a car of this caliber is IMO priceless... bottom line : get the Technistrada cat CUs before anything else. The OEM units WILL fail down the line, it the used units that you have sourced have not already.

Professional mechanics like Brian are supposed to make the best of the stock items and are not supposed to use any non-OEM items for liability reasons. If a car for example burns down because of any issue even unrelated to possibly installed aftermarket items any insurance expert will be all too pleased to put the responsibility on either the owner or the shop that maintains the car, at least in my retarded country and certainly the same in DK where there has never really been a strong car culture in my experience.