355 Airbag going off on its own

Glad you are okay. If could have been a lot worse if you were driving the car.

As to what sensor triggered the Airbag ECU I believe you will need an SDx analyzer or a similar device to determine what sensor set it off. Was there any work down around the steering column? Did only the driver's airbag go off or did the passenger airbag deploy as well?

You don't want to install a new airbag until you figure out why the old one was triggered.

 

The only thing that should trigger it is the accelerometer/switch in the ECU in the centre console.

However, stray voltages in wiring can set off specific airbags. The wiring from the ECU to each airbag is separate... unless someone put a screw through the main harness coming from the airbag ECU contacting several wires... and vibration moved the wires? Looking at graphics of the airbag system, it branches off under the dash.

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Sorry to hear about your injuries.

It's going to be a big job replacing the ECU and wiring.

 

Note that there are two different models of airbag ECU with different plugs/harnesses.

 

Google spontaneous airbag deployment. It just happens…on better built cars. Ferrari wiring isn’t the greatest either and low volume production does not help reliability. I can’t see how you are responsible if there is no impact that would trigger the bag. Airbag replacement life is every 10 years. No one I know does that.

 

Of course, parts are rare and expensive, but unless you can find something which is 100% the cause, I wouldn't be refitting a new driver's airbag.

Unfortunately, we haven't seen any wiring diagrams for the old type Airbag ECU and I'm not confident that the later Airbag ECU has the same pinout to the similar looking 360's ECU. The 360 also has seat pretensioners.

The old type with red plug only has 7 pins, so I suppose it will be easier to figure out what goes where.


I produced a possible diagram for the later Airbag ECU with a yellow plug, but I wouldn't bet anyone's life on it.

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This is looking at the contacts (sockets) on the car harness (not the wire side). Diagram contact colours represent possible wire colours.

I would disconnect the passenger airbag and carry out continuity checks on the driver's wiring (including shake checks)

I assume something will have to be reset in the ECU. Maybe are their specialists who can run tests on the ECU for you.

I assume you know you need a Ferrari SD1 tool to reset airbag lights (including those caused by turning on the key with the instrument binnacle removed).

Anyway, please let us know how you go. We need as much information on this system as possible.

 

I thought the 355 airbag ECU triggered both airbags at the same time.

If that is the case…..this could just be a random airbag deployment and the ECU thinks things are fine except for the resistance being wrong on the driver’s airbag since it was deployed.

If it was me, I would bypass the driver’s airbag with a resistor and put the car back together and reset the light.

If it was just the airbag…..it won’t happen again. If it was the ECU or sensor the light should come on but no airbag gets triggered.

Plenty of threads on Fchat about the correct resistor to be used. $.10 fix allows the car to be used, pass a Safety inspection and provide some more diagnostic info.

I have never been a fan of the airbags in the 355.

 

Sure, but maybe there is some kind of squib driver transistor in the F355 ECU for each bag? Or is it more likely for that to fail than to trigger? Or maybe the passenger squib failed to operate

Squib driver chips come up in Google searches, but no luck for the F355.

At least they can be repaired and reset:

https://crashdata.co.uk/product/169710-ferrari-f355348-airbag-module-repair-and-reset-200029-103/

Check the part number.

 

My understanding how the airbag system works is that the ECU monitors the resistance on the individual airbag circuits. Upon the ECU receiving a signal that the accelerometer/sensor tells it to deploy airbags it applies a minimum of 12 volts (frequently double in most cars to avoid an inadvertent short) to the airbag connection to fire the squibs in both airbags. I do not know what voltage Ferrari uses to trigger airbags in the 355. Since they don't make the airbags.....I lean toward the industry standards that avoided accidental 12 volt discharges.

In this case I agree with FBB that this was most likely a spontaneous deployment which means the ECU did not trigger it. If it had.....it would have fired the passenger side as well. Sure, the passenger side could have misfired but my money is on a spontaneous deployment of the driver's side.

The easiest way to tell is to hook up an SD1 and see what the ECU says. If you don't have access to an SD1 that makes things more complicated since the ECU knows that an airbag is missing (no resistance).....the light will stay on. Even putting a resistor into fool it.....still requires the ECU to be reset.

So the long and short answer to answer this question requires an SD1 to be hooked up to the Airbag ECU. That is probably what the service Qavion recommended is using to reset the ECU. I don't know of another device that will work.

 

I think 3.3 ohms is the preferred value. Someone triggered the light with a 4 ohm.

 

Man that’s sketchy! Spontaneous air bag trigger is crazy

 

That would suck

 

This is assuming your airbag connector hasn't melted.