Another slow down light question

Wait till you see what's inside!! It's amazing. I opened one once.... I found the ashes of Enzo himself, and the remnants of three virgins from Mt. Olympus who assembled it in 1989.

 

o.k. I'm openning up one of mine now.

 

You'll probably find Ernie's soul inside there. I heard he traded it to the devil for a few roller bearings.

 

I carved up one from a 308 that birdman donated with an eye to making the necessary schematics to reproduce the thing if someone desired. In the end, though, it's probably simpler to just redesign a new ecu using a programmable controller with a A/D convertor and some basic I/O. The main trick is properly conditioning the signal from the thermocouple.

While it's safe to say it contained about $10 worth of components, getting the values off them wasn't doable. I'm waiting to get another one, preferably from a 328 where cracking off the plastic may be more rewarding than carving a solid epoxy block. However, even another white one from a 308 would help, since exposing the circuit board side would allow measuring the values of most of the parts.

On the 308 ecu, the only part inside that would be potentially moisture sensitive is a trim pot.

In any case, if someone has a bad ECU they don't want, please PM me.

btw, dirty thermocouple connections can cause the circuit to false trigger, so make sure that's not the problem before doing something more drastic. I see the 348 ecu uses the sealing style plugs, which makes that less likely to be an issue compared to the earlier cars.
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Good post. Ferrari exhaust ECUs expect just less than 800 ohms resistance between those two wires that connect from a cold thermocouple, and anything less than 350 ohms tells an exhaust ECU that the cat is overheating. Anything more than 800 ohms tells an exhaust ECU that you've got a broken wire or other problem (CEL). Anything less than 350 ohms signals overheating (and a short circuit has 1 ohm or less of resistance). So resistance values between 800 and 350 ohms are good, while other values will trigger Slow Down or CELs.

Since the problem seems to be SLOW DOWN lights rather than CELs, I'd think that we're getting a short inside the exhaust ECU itself rather than in the thermocouple or external wires...since replacing the exhaust ecu tends to fix the issue.

Of course, moisture/corrosion could short any two points on a circuit board, or internally short a pot or other component inside the exhaust ecu.

Find the short and we're well on our way to finding a good solution to exhaust ecu failures (other than throw the safety device away).

 

LOL, I don't think so.