348 Exhaust thermalcouple

Some find the SLOW DOWN lights to be useful not only for detecting cat degradation, but a sign that the engine is incorrectly fueled.

I recall that removing both thermocouple ECUs will result in permanent SLOW DOWN lights on the early 348's and maybe more (or different) lights on the later cars fitted with Motronic 2.7 ECUs (experts?). The thermocouple ECUs talk to the Motronic 2.7 ECU (but not on the early cars which have Motronic 2.5).

 

Was it a Euro car? They don't have SLOW DOWN lights.

In theory, it shouldn't trigger the SLOW DOWN light if you remove the cats, but you may have a faulty Thermocouple ECU or thermocouple triggering the lights. What Motronic ECU do you have?

 

https://www.ferrarichat.com/forum/posts/142546533/

Looks like only a silent ECU code is triggered if you disconnect the CAT ECUs on a 2.7 car. No lights.

Ugh... Too many variations. Now we know some Euro cars do have SLOW DOWN lights.

 

Also, some folks have fitted bulbs to their SLOW DOWN and CHECK ENGINE warning lights on their Euro cars for diagnostic purposes. It's not standard on most (?) Euro cars. The wiring for the lights is fitted though.

Maybe Switzerland is more strict than other Euro countries.

 

My 1991 2.7 UK spec came from the factory without CAT-s but with Thermocouples (on the straight pipes), control boxes and SDL-s. Works fine with the control boxes disconnected, no SDL-s or CEL-s (only "silent" codes).

 

My 348 had all provisions for reading of engine codes except the push-buttons at the ECU-s. After I installed the push-buttons, I read the codes and found 4121 ("Catalyzer temp ECU") on one side. Bench testing the temp ECU from that side confirmed it was bad (the old, black resin, Vescovini) so I left both ECU-s disconnected. Later, I adapted and installed two 355's (green resin) exhaust ECU-s to work on 348. I set them to blink the SDL-s but not to shut-down the banks.