XKR 100 Air Bag - Seat Occupancy Sensor FaultHi I'm a New Member to the forum with an XKR 100 2002 Convertible which is a dream to own and drive and always draws attention.
I am looking for any pointers or answers to an airbag dashboard warning light that I am unable to clear and is an automatic MOT fail
I have had a professional airbag company run a diagnostic and it came up with a seat occupancy fault which spare part proved to be unobtainable and discontinued by Jaguar
Resourced a genuine second-hand unit which was accepted by the diagnostic tool but refused to clear the fault. Several people suggested earthing the positive battery lead to the chassis this also failed to clear the fault. Then I replaced the Airbag ECU located in the driver's footwell bolted to the chassis which also failed to clear the fault.
As the MOT has subsequently run out I am looking for anyone who has managed to solve this problem, please help?

 

Does the airbag light flash a fault code? If you count the flashes you can then look up the fault yourself and post it on here for better advice. If you have replaced modules and it still doesn't work, have you checked all the seat wiring for broken/chafed wires?

 

 

I could be wrong, but I thought the flash codes were two digits? Once you have the code you should be able to find more information on the forum.

If you are sure the drivers/passengers modules can be swapped that would certainly help prove where the fault lies.

I would still be looking at the wiring/connectors though - can you check for broken wires with a multimeter?

 

Btw the wiring diagram for my car shows:-

Occupancy sensing module
Passenger seat weight sensing module
Passenger seat weight pressure sensor

What did you replace?

 

The airbag flash codes are indeed two digits. Sounds like the flash code has been misinterpreted....

 

Hi, dibbit/Jon89,
Thank you the flash codes were interpreted by the Airbag specialist using a Jaguar diagnostic tool but will check with him as to what the two-digit figures are? As I understand it once the ignition is turned on the car runs its own diagnostic and initially goes out then the airbag light comes back on and flashes a number of times quicker (which in this case is 6) which is recognised by the diagnostic tool plugged into the car's system
Similarly, as the diagnostic tool recognised each of the sensors this proves the wiring circuitry as true but will look into testing with a multimeter as you suggest
The sensors I've replaced are the Seat Occupancy Sensor (located in the seat cushion between the leather and the foam and looks like flat bubble wrap) and the main Airbag ECU control module
On this basis, this leaves the weight sensing module and the pressure sensor to be checked which I intend to substitute with the driver seat units if compatible to rule out?
Again your comments would be greatly appreciated

 

The first thing to do is work out what the flash code is - the airbag warning light will flash when you turn the ignition on. It will flash, pause, and flash again - these are the two digits for the code. It does this a number of times before going steady. You can do this yourself, then look the code up on here. You should also ask the specialist you took it to what the actual codes were that he read, so you can look them up yourself.

You also need a wiring diagram for your car - my 2001 convertible wiring diagram shows the pressure sensor itself (I guess that is the part in the seat) which has three wires going to the sensing module (which I don't think you have changed). There are no equivalent parts for the drivers seat as they aren't needed. I would be checking all the wiring that goes to the seat.

Edit: here is the wiring diagram for the airbag system - this should be for your car (check the vin number)

And make sure to disconnect the battery before doing anything.

 

Hi Dibbit, Thank you for your time and advice very much appreciated.
Armed with your comments I will check my car ignition and report back with the two figure code, you say look up the code here, where will I find the respective fault? Equally, I have requested the same from my airbag specialist. Yes, your wiring diagram does indeed conform with my vin number, thank you. Agreed the passenger seat weight pressure sensor would be the seat unit which I've changed (twice now - in case the first was faulty) and the occupant sensing module but not the weight sensing module, this seems to be worth changing now along with checking respective wiring that goes to the seat as suggested?
I note your comments regarding equivalent parts for the driver's seat and disconnecting the battery before doing anything.

 

Once you have the code do a search on the forum - if you browse the forum on a desktop computer there is a "search this forum" button fairly well hidden at the top (just above the list of threads, not the generic search box at the top). Or you can just do a google search,eg "jaguar xk8 airbag fault code XX" and see what you find.

Post the code on here as well and others may have experienced the same fault.

 

Check this for background: TSB XK8/501-T836.pdf

This is for Diagnostics: 501-55 SRS Flash Codes.pdf

Seems to suggest these occupancy sensors are really the ultrasonic devices in the pilars and upper console. Separate from the seat switches you have already replaced.

This is an EXCELLENT thread: /air-bag-code-17-a-94959

Goes without saying that you NEED these codes to get started down the right path...

 

A visual inspection of the seat wiring will not necessarily show the fault.

I have an intermittent airbag fault with the seat belt buckle wiring that I need to fix. The fault shows up when the seat is fully lowered, in this position it pinches the seat loom. Raise the seat half an inch and the fault disappears.

 

 

Have you double checked this Fuse 14?

 

 

 

I would suggest downloading the workshop manual (you can get it as a PDF) and looking in there for the location of the module and then you can read the part number of your own module - although I still think a chafed or broken wire is a more likely cause.

Have a look at this on Gus' site with some pointers to where everything is:-

http://www.jagrepair.com/images/TSB/XK8/501-T836.pdf

Oh and make sure you check that fuse and hope that that is the problem

 

Hi fmertz, Thank you for your suggestion regarding Fuse 14 reference B2290 (26) I double checked this today with multi meter and all good but well worth a try was quietly confident this would be the nemesis �� Seems I need to revisit possible chafed wires, �� How does this work do you test open circuit.

 

 

That same document has one more hit:


There is patience involved, but the electrical guide will have the detail about these connectors. They are typically listed in the wiring diagram itself, and then one page before in the index, along with some clue as to the location. There is also a page that lists the (approximate) location of each control module early on in the book.