360 - Inter-ECU CAN Bus Wiring | FerrariChat
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360 Inter-ECU CAN Bus Wiring

Discussion in '360/430' started by Qavion, Apr 30, 2025 at 7:45 PM.

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  1. Qavion

    Qavion F1 World Champ
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    Ian Riddell
    #1 Qavion, Apr 30, 2025 at 7:45 PM
    Hi, folks, just wondering if there are any 360 CAN Bus gurus out there.

    There is a CAN Bus between the Left and Right Motronic ECUs. Half way between them is an inline connector labelled "18G/14G". Various 360 WSM wiring diagrams (unusually) show a single 120 ohm termination resistor on the LH ECU side of the connector and none on the right side of the connector. However, when wiring checks are done from the plug halves to their corresponding ECUs, 120 ohms is measured on both halves. This has been confirmed on two cars.

    Checks have only been done with the ECUs plugged in. We are not sure where the termination resistors are. Are they:

    1) in the wiring somewhere close to the ECU connectors?
    2) inside the ECU connectors (I've seen this on the 355F1)?
    3) inside the ECUs themselves, between pins 45 and 61 on the inboard connector (LH ECU) and the outboard connector (RH ECU) on the Modena? On the Spider, this corresponds to the lower and upper plugs on the LH and RH ECUs respectively.

    Perhaps if someone has a spare ECU, they could measure across these pins?

    Image shown of wire side of harness connector, so should correspond to the pins on the ECU:

    Image Unavailable, Please Login

    Thanks!
     
  2. eric355

    eric355 Formula 3
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    #2 eric355, May 1, 2025 at 6:54 AM
    Hi Ian.
    In fact there is only one CAN bus on the 360, hence only 2 termination resistors "close" to the physical extremities of the wires.
    The CAN bus between the 2 ECUs is the same as the one going to TCU, dash, ABS.
    I made some measurements on one ECU : pin 29 and 45 are connected together internally (CAN bus H), pin 12 and 61 are also connected together internally (CAN bus L).
     
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  3. Qavion

    Qavion F1 World Champ
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    #3 Qavion, May 1, 2025 at 7:43 AM
    Fascinating. Thanks Eric... It all makes sense now.


    Cheers
     
  4. ItsAboutThatTime

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    #4 ItsAboutThatTime, May 1, 2025 at 8:50 AM
    I'm always hesitant to respond to more technical posts like this, but I do take pride in knowing that in terms of "normal" vehicles, I'm pretty darn good at CANBUS diagnostics. With that note, hopefully I'm not speaking out my who-ha.

    So speaking in terms of normal cars, there are typically two resistors through the entire CANBUS circuit: one in the single ECU and another in either the BCM or more commonly the instrument cluster. When I'm chasing CANBUS issues I unplug the battery and check resistance at pins 6 and 14 of the DLC, and if it shows roughly 60 ohm, then wiring for the whole circuit is considered intact (two, 120 ohm resistors in series halves the value)

    Granted I do not have the knowledge of Ferrari you do, I'm wondering if when you measure the left side ECU you're getting the obvious labeled resistor, but when measuring the right you're getting the other resistor somewhere else in the circuit. Despite the splice being undone, is there another pair of CANBUS out of the ECU? I'm wondering if you're separating ONLY the communication between the two ECU's. You mentioned that the 14G/18G splice is able to be undone - you could technically check the wiring from the splice to the undone connector at the RH ECU, and you could also go directly to the RH ECU pins themselves to see if there is an unlabeled one in there.

    With the notes from Eric and the way he made some measurements, resistors are placed between the high side and low side, so by mentioning there are two pins for CAN High and two pins for CAN Low, it would suggest that there are two twisted pairs instead of just one?

    Just my two cents and some thoughts for you.

    - Shane
     
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  5. Qavion

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    #5 Qavion, May 1, 2025 at 9:53 AM
    Well, visibly, it looks like there are two CAN Busses and two twisted pairs, but basically, there is only one twisted pair which goes from the LH ECU to the RH ECU and through the RH ECU and on to other ECUs. There can't be a resistor in the RH ECU as that would be a third 120 ohm resistor. The other resistor is at the front of the car (at the ABS ECU end).

    I think Ferrari have put at least one resistor in the Left hand Motronic ECU connector (26L) not in the ECU itself. This is based on my experience with the 355F1.

    Note that the ECUs are hard to get to on the Modena, so we are doing resistance checks from the inline plug between the two ECUs (14G/18G), not actually checking at the ECU plugs.

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    Indeed, we are disconnecting the 14G/18G plug and measuring in both directions and getting 120 ohms in each case. Also, when we backprobe 14G/18G with the plug connected, we get 60 ohms.
     
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  6. flash32

    flash32 F1 Veteran

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    #6 flash32, May 1, 2025 at 10:11 AM
    Ian,,

    What type of issues / symptoms / error codes are you trying to resolve ? I am curious to know for future reference

    Thanks
    Dominick
     
  7. eric355

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    #7 eric355, May 1, 2025 at 12:10 PM
    I confirm that there is no (termination) resistor in the ECU between CAN-Hi and CAN-Lo.
     
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  8. ItsAboutThatTime

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    #8 ItsAboutThatTime, May 1, 2025 at 12:30 PM
    No problem, thanks for filling me in. I'm here to learn as much as I can but try and contribute as well. Unfortunately my experience falls completely outside of the exotic world but some of it translates over. Good luck with the potential issue you're chasing
     
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