Airbag warning light and can bus errors… | FerrariChat
Buy

Airbag warning light and can bus errors…

Discussion in '612/599' started by LondonParis, Aug 4, 2025 at 1:03 PM.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, Skimlinks, and others.

  1. LondonParis

    LondonParis Formula Junior
    Rossa Subscribed

    Sep 30, 2020
    508
    Houston/London/Paris
    Full Name:
    Bill Coates
    #1 LondonParis, Aug 4, 2025 at 1:03 PM
    I have an intermittent airbag warning light that I am chasing…

    For context, 2009 612 OTO, 157500 kms (98,000 miles)….car is used everyday.

    Error is “Driver side airbag 1st stage”. I have run the live data off the trw airbag ecu and the 1st stage resistance when no code is triggered us 3.0-3.5 ohms versus the expected 2.0 ohms. The drivers airbag 2nd stage shows 3.0 ohms. Passenger side airbag and all the pretensioners show 2.0-2.5 ohms.

    When the fault is present, the 1st stage driverside resistance is reading 4.5 ohms. The fault will occur for as little as a few seconds up to about 20 minutes maximum and then it clears itself.

    Adding some intrigue, about 10% of the time the airbag light is on, a can bus errors occurs causing momentary issues with the fuel sender and other items on the can b data bus. These are all fleeting but scanning afterwards you may find errors with the door ecu, the ceiling ecu…etc all saying can bus error.

    None of these issues cause problems with the drivability of the car…she just cruises along without missing a beat.

    What I have done so far…

    1) changed the battery
    2) pulled the airbag and cleaned the connectors
    3) cleaned the connectors under the seats…

    All to no avail…still have higher than expected resistance on the drivers side airbag circuits.

    So next up…getting to the airbag ecu. I have the WSM but does anyone have some guidance on the easiest way to gain access so I can pull and clean those connectors.

    I am also hoping someone has the wiring diagrams for the airbag system so I can track down the intersection point of the airbag fault and can bus error.

    Thanks…

    Bill

    Image Unavailable, Please Login
     
  2. brogenville

    brogenville Formula 3
    Rossa Subscribed

    Apr 24, 2012
    2,275
    UK
    Full Name:
    Robin
    #2 brogenville, Aug 4, 2025 at 7:33 PM
    Hi bill, the errors with the canbus and the airbag seem like separate, but possibly related issues. As you probably know, the airbag system uses its own “fault tolerant” canbus, but it’s conceivable that there is a multi plug somewhere that’s corroded maybe, and is causing both the B-can interference and the high resistance in the airbag circuit?

    I’ll try to get some time to dig out the wiring diagrams for you that relate to the airbag systems.
     
    mike051 likes this.
  3. brogenville

    brogenville Formula 3
    Rossa Subscribed

    Apr 24, 2012
    2,275
    UK
    Full Name:
    Robin
    #3 brogenville, Aug 5, 2025 at 5:55 PM
    Right, so I looked up the airbag wiring. I was convinced there was an A-can for the airbag systems, but it looks like I was mistaken - the airbag in in fact on the B-Can network (the same one as used by the ceiling module, AC, driver/pass seats and others). See below:


    Image Unavailable, Please Login
     
  4. brogenville

    brogenville Formula 3
    Rossa Subscribed

    Apr 24, 2012
    2,275
    UK
    Full Name:
    Robin
    #4 brogenville, Aug 5, 2025 at 6:00 PM
    I guess its possible then that a fault on the B-can, could lead to all kinds of wierd error messages relating to these modules. Its interesting to me though that there is a fault listed with the pass airbag. I wonder then if its possible that the airbag ecu has gone all screwey, hence the resistance fault, and the same general screweyness is causing intermittent faults on the B-can network?

    Below are a few more screen shots from the Ferrari interactive WSM relating to the airbag systems.


    Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
     
  5. brogenville

    brogenville Formula 3
    Rossa Subscribed

    Apr 24, 2012
    2,275
    UK
    Full Name:
    Robin
    #5 brogenville, Aug 5, 2025 at 6:03 PM
    On an unrelated note, if you fancy putting a car seat in the front of you 612 and want to inhibit the airbag, it looks likely that to inhibit the passenger airbag, all you need to do is wire the standard Fiat group airbag switch (same one as used on a cheap Punto) into ground and pin 9 on plug B of the airbag ecu. :)
     
  6. LondonParis

    LondonParis Formula Junior
    Rossa Subscribed

    Sep 30, 2020
    508
    Houston/London/Paris
    Full Name:
    Bill Coates
    #6 LondonParis, Aug 6, 2025 at 2:03 AM
    Robin,

    Thank you.

    The diagrams confirm exactly what I have been seeing once the airbag fault occurs, extraneous errors along the can B module chain. I really need to get access to the airbag ecu to see if it is a connection issue or if the ecu is going out (my gut says grounding issue).

    Do you have any idea how to pull the BOSE NIT from the dash? I need to remove the passenger footwell trim piece between the glovebox and the center tunnel and the top screw is behind the BOSE. The wsm version that I have has instructions for the single DIN unit.

    Regarding the passenger airbag, my OTO has the option OFFP, which is the airbag disable switch but good to know the aftermarket option exists.

    Bill
     
  7. mike051

    mike051 Karting

    Jan 21, 2019
    91
    #7 mike051, Aug 6, 2025 at 4:07 PM

Share This Page