What is this?

Hi, it looks as the 2 ECUs that monitorize the temperature of the catalyzers (and eventually turn on the "slow down" warning light...) has been jumped.
These ECUs are a pretty common fault of our cars, there are many threads about "slow down" warning light.
If your car is running without cats, that is not an issue at all, but if you do have cats, I'd fit new ECUs, which are not that expensive after all...

 

Sorry...silly me! Forget what I wrote...that is NOT the cat ecu plug... No Idea what it's for, but on my 1997 Europen 550 it is "jumped" with an original cable, with no visible resistance through it...

 

Is that a resistor in the jumper wire? If the colour code is brown-red-brown-gold (120 ohms), it may have something to do with the right bank engine ECU to left bank engine ECU datalink.

It's shown in the wiring diagrams...

See equipment number 152

Ferrari_550_Right_Bank(1~6)_Injection

At first I thought it might be a jumper for daylight running lights, but that has different coloured wires.

 

Does your 550 have Canada daytime running lamps?

 

The daytime running lights jumper for my 550 is next to the fuse box in the right side foot well.

 

Yes, that is normal, there are two connectors in the ABS system that are jumped like this. The bundle of wires next to it is the ABS ECU harness. Parts #19 on the ABS diagram here: https://www.ricambiamerica.com/car-diagrams/ferrari/v12/gt-group-2-seat/550-maranello/control-unit-and-hydraulic-equipment-for-abs-asr-system.html

 

What’s funny is the 456M uses the exact same ABS ECU, but it does not have any jumpers.

 

Mine is 99 and has the same thing

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What are the wire colours on the other side of the jumper? Yellow, black and ???

Looking at the 550 wiring diagram for the ABS/ASR, the only 3 pin connector with yellow and black wires has the strange label "Connecting joint between ABS/jumper or electric actuators".

Ferrari_550_ABS_&_ASR_Wiring_Diagram

 

Very strange! I seem to recall the jumper has a specific resistance as well, like 15ohms, so it must be defeating/neutralizing something in the system that is active in the 456M.

 

I think it's a Canbus resistor. It may be enabling rather than disabling something.

For the technophiles...

https://www.ni.com/en-au/innovations/white-papers/09/can-physical-layer-and-termination-guide.html

"High-speed CAN is the most common CAN transceiver. It is used in nearly every production automobile and is required in model year 2008 and later On-Board-Diagnostic (OBD-II) vehicles sold in the USA. "

"
High-Speed/FD CAN Termination
For high-speed/FD CAN, both ends of the pair of signal wires (CAN_H and CAN_L) must be terminated. This is because communication flows both ways on the CAN bus. CAN_L is pin 2 and CAN_H is pin 7 on the standard 9-pin D-SUB connector. The termination resistors on a cable should match the nominal impedance of the cable. ISO 11898 requires a cable with a nominal impedance of 120 Ω; therefore, you should use 120 Ω resistors for termination. If you place multiple devices along the cable, only the devices on the ends of the cable need termination resistors."