355 - Electrical issue car shutting down, fault possibly found? | FerrariChat
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355 Electrical issue car shutting down, fault possibly found?

Discussion in '348/355' started by Ben111, Apr 17, 2025.

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  1. Ben111

    Ben111 Karting

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    #1 Ben111, Apr 17, 2025
    My 355 will randomly shut down whilst driving, the engine, instruments, windows seats etc all switch off, the only electricals which work are the central locking, alarm, hazard lights and cigarette lighter.


    I have take the steering column out and found this,

    the yellow cable runs into an orange connector, and then the cables from this connector are in a bad state, it then runs through into the top of the wheel as marked in red.

    what is this lead for, and could this be causing my issue?

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  2. 308 GTB

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  3. Qavion

    Qavion F1 World Champ
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    #3 Qavion, Apr 17, 2025
    Usually yellow-sheathed cables are associated with the airbag system. The Airbag ECU is powered by the Instrument fuse, but I wouldn't expect a short on the steering wheel airbag to take out everything on the instrument fuse, just affect the Airbag ECU. But I doubt even a blown Instrument fuse would stop the car running.

    To be honest, I've never seen this kind of damage to airbag wiring. If this wiring shorted to a power wire, it could blow the airbag.

    With all those symptoms, it sounds more like an ignition issue. I guess that's why you were pulling the steering column to pieces.

    Were there any other issues before this? Have you had an engine out recently? Do you have a Motronic 2.7 or 5.2?
     
  4. Qavion

    Qavion F1 World Champ
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    #4 Qavion, Apr 17, 2025
    I see the Instrument fuse powers the speedometer which sends vehicle speed data to the Motronic ECU (and the F1 TCU where applicable). I don't know how reliant the engine ECUs are on vehicle speed.

    WSM:

    Car speed signal
    + This is used by the ECU in combination
    with the throttle potentiometer
    signal to discriminate between the car
    stationary and “release” conditions.
     
  5. Ben111

    Ben111 Karting

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    #5 Ben111, Apr 18, 2025
    Last edited: Apr 18, 2025
    So the issue in more detail.

    when it happens I lose all the electrics other than the central locking, cigarette lighter, Hazard lights, alarm, the rest of the car is completely dead, I will turn the key multiple times and regardless of the ignition position there’s no sign of life at all, not a single thing, eventually the car will “wake up” I’ll get the electrics back and off I’ll go, note I do not do anything to “resolve” the issue during this time.

    it first happened in 2022 , I was driving and all off a sudden the car switched off and I rolled to a stop, 15-20 minutes later it came back to life, it was fine after this.

    1 year later the exact same thing happened, it came back on a couple of hours later, this time I investigated and found the battery terminals to be corroded and loose, so I replaced the connections and installed a new battery hoping this was the cause.

    then last weekend I broke down 3 times with this issue
    - breakdown 1, I stopped to get fuel and when I went to turn the car back on the issue was present, 30 minutes later it resolved so I headed home
    - breakdown 2, 10 minutes later whilst driving the issue came back and I rolled into a car park, it resolved itself in 30 minutes and I continued the journey home
    - breakdown 3, around 20 minutes from home the cars electricity died again, this time I was stranded for 2 hours and I ended up getting towed home.

    the following morning back in the garage the car starts fine as normal, due to the nature of this issue I have lost complete confidence in driving the thing, it’s borderline dangerous at this point not to mention embarrassing.

    The engine hasn’t been out since 2021, although note the issue first came in 2022.

    also bare in mind although the issues happened 5 times now, 3 of those were on the same day at the weekend, the other 2 times were a long time apart, the car is usually frequently used, I.e multiple times per week

    I started with the steering column due to the fact the electrics which continue to work during the issue are different feeds, as far as I’m aware everything I lose stem from the ignition?
     
  6. cactussed

    cactussed Formula Junior

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    #6 cactussed, Apr 18, 2025
    Had a vaguely similar issue some time back. Car would die completely. Turned out to be very badly corroded earth wire to the battery. Replaced the cable and all resolved, so maybe worth checking, although the fact some bits stay active seems v odd. Mine would die completely...

    My guess is(and it is a guess) is that the circuits described operate with their own earth (and thus circuit) whereas the rest of the car is a separate circuit.

    Sadly, I can't point you towards the separate earth...
     
  7. Qavion

    Qavion F1 World Champ
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    #7 Qavion, Apr 18, 2025
    Seems to be the case. I can't tie the issue down to a particular fuse/relay panel. The Immo ECU does get an input from the ignition key (but I don't know what its function is). There are 3 other power sources going to the Immo ECU.

    Anyway, I would get some silicone tape and wrap up those airbag wires. I can't believe the way the insulation has cracked. Was the car cooking in Death Valley? (I see you have a US import).

    Unfortunately, unless you can reproduce the fault in your garage, we're not going to make much progress. I was going to suggest leaving the covers off the relay panels and seeing which fuses had no power next time it happened. Check fuse 24 (AC) in the footwell first with the key on. That power comes directly from the ignition key. If you have power there, the ignition key should be ok.

    The issue may even be the live battery power supply going to the ignition key. If you can backprobe the car side of the plug, the red wires should be live. The white, yellow and blue wires should have power with the key on.

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    Still, the ignition switch doesn't strike me as something which breaks down then fixes itself 30 minutes later. It sounds like something is overheating, then cooling.
     
  8. Ben111

    Ben111 Karting

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    #8 Ben111, Apr 18, 2025
    The car is from Miami, I was hoping those cables would somehow be causing the problem, rather than applying tape couldn’t I have have it unpinned and new cables, or is this a bad idea with it being connected to the airbag?

    The problem is I don’t know when the issue will next appear, if it was likely to happen everytime the car warmed up I’d happily have it idling on my driveway, but it could be fine now for months, or maybe not with it repeating the issue 3 times the same day at the weekend.

    If something was overheating, would this not happen everytime I used the car? If we just count last weekend as being one event, the issues appeared 3 days out of the last 3.5 years.

    Also like I said, I’m very hesitant to drive the car now, there’s no warning of it about to happen, so I could be at some traffic lights, a motorway, a fuel station or a nice quiet road, there’s no telling.
     
  9. Qavion

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    #9 Qavion, Apr 18, 2025
    If not heat, then rain?

    You could have anything done at great cost. It seems like you'd have to pull the car to pieces to put in new wiring (centre console, dash, etc).

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  10. Ben111

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    #10 Ben111, Apr 18, 2025

    The wiring pre the orange connector looks to be ok, (although I’ll have to give it another once over). The damage is post connector and then into the wheel, I thought it would be better to replace the wiring post connector, not the whole lot
     
  11. Qavion

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    #11 Qavion, Apr 18, 2025
  12. Ben111

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    #12 Ben111, Apr 22, 2025
  13. Ben111

    Ben111 Karting

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    #13 Ben111, Apr 22, 2025
    Also there isn’t a separate ecu for the ignition is there? I’m assuming this is part of the main ECU located behind the passenger seat ( 5.2 so
    Only 1 motronic)
     
  14. Qavion

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    #14 Qavion, Apr 22, 2025
    Relay P only controls the power to fuses 25 and 26 and power to the coils of relays Q & R

    25: Turn and reverse lights, cigarette lighter (on some cars), window and mirror heat
    26: Windscreen wiper and brake lights.
    Relays Q & R are for radiator fan control.

    Seems you have a lot more not working than these items. Brake lights can affect the F1 system, but not shut down the engine.

    Your issue seems to be further "upstream", closer to the key.
     
  15. Qavion

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    #15 Qavion, Apr 22, 2025
    If you can reproduce the issue, pull that P relay. You should have no power on the relay socket coil contacts (85 and 86) with the key on (if the problem is with the ignition key wiring) or just check for power on fuses 25 and 26 with the key on. Most old fuses have cutouts in the plastic for testing voltage in-situ: Put one voltmeter probe to the top (or bottom) of the fuse and the other probe to a good ground.
     
  16. Ben111

    Ben111 Karting

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    #16 Ben111, Apr 22, 2025
    Ok thanks again, as I say the problem is I’m reluctant to drive the car due to the uncertainty of when and if it will break down, there’s only
    So many roads close by i could suitably break down in peace and safely perform roadside diagnostics!

    My neighbours would complain if I left the car idling for a sustained amount of time, although I would do
    If the issue was guaranteed to happen.

    really is a nightmare!
     
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  17. Qavion

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    #17 Qavion, Apr 22, 2025
    Yeah... understood.

    All I can suggest is doing wire shake checks whilst monitoring voltages. Shaking might reproduce or exacerbate the issue.
     
  18. yelcab

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    #18 yelcab, Apr 26, 2025 at 9:08 PM
    Very early on when I started with the 355, there was a similar/identical issue on a 355 that would randomly not start, just dead. The problem was solved when you reached under the steering wheel column and wiggled a wiring harness until it started. The culprit was a loose wire on one side of the connector pair.

    If I were you and the symptom repeated itself, I would start wiggling and moving wires under the steering column and if car started again, I would focus on wires there. I know there are a lot of wires under there, but .... you gotta start somewhere.
     

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