Slow down light 5-8

It means 1 of 3 things

1) The catalytic converter on the 5/8 bank of cylinders has gotten out of the temperature tolerances

2) The catalytic converter ecu is not getting the signal from the thermocouple (that is the temperature probe inside the cat)

3) The Motronic ecu is getting a false signal from the Cat ecu (usually meaning that your cat ecu is malfunctioning)

Since you have a '95 you have the Motronic 2.7 ecu's. This will make the job of figuring out if you have a bad cat ecu easier. What you will want to do is swap the cat ecu's from one side to the other. It's an EASY job you can do yourself. After you have swapped the cat ecu's from one side to the other take the car for a drive to see if the light jumps sides to the 1/4 bank. If it does then you know that the ecu is bad. If it doesn't then you will need to perform the same swap with the thermocouples. If after that you STILL get the slow down light on the 5/8 bank then you indeed have a problem with that bank running rich causing the cat to over heat, and will need to address that issue. But I have my money on the cat ecu being bad.

Run a search of the archives if you need more info as this has been discussed many, many, many times.

 

Here's a related question (sorry if this is too far off-topic): has anyone ever rebuilt a bad cat ECU? I have a 1982 gtsi with (I believe) a bad ECU. What goes wrong with these things? Is there a printed cicuit board in there that corrodes and goes bad or ???

 

Ernie is giving you the advice you need.

The only thing I'll add is a basic description of what's going on just in case you do not understand the system. The Slow-Down light is designed to warn you of dangerously high heat in your catalytic converter. But since you say it is flashing when the car is cold, then of course it cannot be the case that the Slow-Down light is functioning properly.

However, it could also be the case that you have problems when the engine is warm -- but we do not know that yet. We will only know that if we get your Slow-Down lights to function properly. But since you have not mentioned any Check Engine lights, which are supposed to present a warning of the first stage of overheating before the drastic Slow-Down light stage is reached, we must tend to assume that there are no problems warm.

At this point, it is safe to say you definitely have a physical problem with something somewhere. Most likely, it is with either the thermocouple (temperature sensor) or the thermocouple control module (or "cat ECU" or "thermocouple ECU"). Could be just corroded connections that need cleaning. Try what Ernie says and get back to us. While you're at it, clean those electrical connections really well with the proper materials.

If you are not inclined to do this yourself, then take the car to your Ferrari technician.