I've had this fault for months now and, with the recent changes in the UK annual test (MoT) regulations from March 2013, its means a fail.

I must start with a big THANK YOU to Trevor (smithtrevor) who shared his experience with this same Code over an equally lengthy period before identifying the cause.

The Code 17 fault sequence on startup is:

1. Ignition check lights all illuminate correctly
2. all check lights go out
3. Instrument Pack Air Bag warning light sequences Flash Code 17 three times
4. Instrument Pack Air Bag warning light stays on

Code 17 is difficult to troubleshoot even with Mongoose or AutoEnginuity as the following troubleshooting demonstrates. The background to Code 17 is covered in TSB (Technical Service Bulletin) JTB00061 - SRS Flash Code Diagnostics. It is triggered by a fault in Occupancy Positioning sensing, calibration or comms.



The four sensors (items 1, 3 & 5) are identical for both Coupe and Convertible except that since the Convertible has no B-Pillar, the equivalent sensor is mounted in the rear quarter trim capping.

The sensors use ultrasound at 40 kHz to monitor passenger front seat occupancy. In troubleshooting the issue I have previously:

1. replaced Fuse #F4 for the SRS (Supplementary Restraint System)
2. substituted the four sensors with known working ones from another 2005 XK8



3. fitted my four sensors in the another XK8 to check they are working
4. checked harness and connectors for continuity and faults to ground



5. substituted RCM (Restraint Control Module)

This narrowed the fault down to the Air Bag Control Module (item 17) or calibration issues.



The Air Bag Control Module is checked as follows:

1. verify the passenger airbag warning light (item 16) illuminates during the start up check sequence
2. check the passenger seat weight sensor (item 13) is working. Do this by sitting in the passenger seat wearing the seat belt and with the ignition in position 2 then lifting your weight off the seat cushion.
3. move the seat forwards until your knees tough the dashboard
4. lean forward for a minimum of 5 seconds so the A-Pillar and Overhead Console sensors should pickup your are too close to the Airbag for safe deployment.

The normal result is the PAD (Passenger Air Bag Deactivation) indicator (item 16) will illuminate. If there is NO light, this indicates an issue with the Air Bag Control Module.

The Air Bag Control Module (HJE 9680 AE) is located on the right hand side of the instrument panel. It constantly monitors the signals from the occupancy sensors and makes the data available to the RCM via the CAN network.

As with the majority of SRS components, it is a non-serviceable item and the only fault rectification is by replacement. Current cost from Jaguar in the UK is £441. I sourced one from a specialist Jaguar breaker for £60.

Removal comes with all the usual warnings associated with working on the Air Bags and is detailed in JTIS Air Bag Control Module 76.73.41:

JTIS - XK8 Air Bag Control Module.pdf

What JTIS doesn't make clear is just how difficult this Module is to access. I removed the driver's seat to give more room to lie on the floor under the dash.



The Module bracket is attached to the body with three 10mm bolts and the Module attached to the bracket with three 7mm bolts. This pic gives an indication of the amount of wiring obscuring the fixings. The Air Bag Module is arrowed in red:



It would be a little easier on a LHD vehicle with no pedals in the way but that bonus is discounted by having to remove the Glove Box!



With the replacement Air Bag Control Module fitted and everything put back together, the Code 17 was gone. The stored DTC remained until codes were cleared with my AutoEnginuity.

So what was the fault with the Module? Here is the cover removed to show the circuit board:



Notice the damage in the centre of the board. Here is that section enlarged:



Not only does it look beyond repair but the concern is what caused both mine and Trevor's to suffer exactly the same failure. This has the potential to be an issue for all 4.2 owners.

Graham

 

Thanks for the write up, it's good info to file away, just in case.

Also good to hear you finally got the problem resolved, even if it was a real PITA to fix.

It is suspicious that you have examples of two identical failures. Can you work out what that bit of the circuit does?

 

Charlie,

I haven't had the opportunity to investigate what that section of the circuit does yet but I'll be tracing it this week.

As you say, two identical failures is suspicious and putting an issue like this into the dealer would result in a very large bill.

The module from any other 2003 onwards XK8/XKR appears to be plug and play with no reprogramming involved because they were all programmed the same at the factory during the vehicle build. However, this isn't the case with a new one from Jaguar - it has to be programmed.

Graham

 

Could do with some higher resolution images, Graham.
The burnt component looks like a highish power surface mount resistor.
You could check its neighbour to the L with an ohm meter.
What are the white things that look like octal valve bases?
My guess would be a short to earth on a harness somewhere with the usual Jaguar lack of over current protection on a driver.
The risk, of course, is an intermittent short frying your new board.
As you say you need to trace the brewed component to a pinout.

 

I was thinking either that or a surge? The possibilities for a short are high as several major harness items are squashed into that area of the dash.

Perhaps co-incidentally I have had a major blow on the Instrument Pack bulbs in the past:



There is some serious overheating damage on that bulb holder.

When I trace the module pinouts, I'll then try to follow the actual harness to see if there's any physical damage.

Graham

 

Thanks GGG for the excellent write up on our shared code 17 fault. I to would like to know the origin of the fault, it really does look like an excessive amount of current drain through the circuit board. You probably guessed I work for FORD UK & at the time of our vehicle builds Ford owned JLR so I had some clever knowledge help with the investigation.
Jaguar know about this issue (I made sure of that) but as with all major manufacturers they will not do anything unless there are enough of us to complain. I just hope somebody on the Forum is into electronics and come up with a "in line fix" either that or somebody will make a mint out of selling OPS modules!!

 

I attach a copy of my failed module for any electronics wizards

 

Need higher resolution pix!!
If we can work out what pin this goes to we can sort out what the module is trying to do.
It sounds daft but maybe a low value in-line fuse would be all the protection needed.
It takes quite a while to fry a resistor (unless the resistor fries because of a blown driver).

 

Trevor,

Is this module a Jaguar specific application or is was it used elsewhere in the Ford range at the time?

Graham

 

Many thanks to Graham and Trevor for their persistence and diligence in finally identifying their Airbag Code 17 demons. As Graham said, having to pay a dealership to effect this repair would be painfully expensive. I sincerely hope that the root cause can eventually be determined. If it indeed turns out to be random electrical surges, these initial repairs may prove to be temporary until a permanent fix is successfully identified. A very scary thought indeed given the amount of work and money involved....

 

Steve,

I'll eMail you a couple of higher resolution pics. The file sizes are too big to post on the forum.

Here's the pinouts on the FC10 26-Way connector:



The circuit diagram is 18-2 in Advance Restraints System:



Included for reference only - it's easier to see it in JTIS!

Graham

 

What do those 'octal' things do- are they connectors ?

 

YES - the lid is secured with 5 small torx screws.



Those 'octals' reinforce the bottom three fixing points.

Graham

 

A quick look at the wiring suggests that (unusually) the impact sensors do not short to ground but between two pins on the module.
If this resistor is in the feed then a short to ground in the harness would fry it.

 

I think the resistor is the culprit.
The orange/brown things everywhere are surge arrestors (to prevent the airbags firing on a whim) so I doubt the problem is a surge.
Can you check the driver transistor (arrowed)
http://www.datasheetcatalog.org/data.../129268_DS.pdf
Using the datasheet and your meter on resistance you should NOT see a short between emitter and collector.
On the diode range you should see 0.6 between emitter and base and base and collector with the terminals of the meter one way round and OL with them reversed.

Is the module mounted vertically with the top at the bottom of the pic attached?

 

No...Ford never took up this option in it's range (in europe).
As far as I know Jaguar and possibly BEMA took up the idea from the US where it originated fro. Somewhere on the net is a write up from the company
That patented the idea.

 

Steve in France do you want me to post the burnt out module to you, so you can have a play? If we get a cure for this problem our wallets can rest easy in our pockets!! PM me with an address and it's on it's way.

 

Fine, PM sent.

 

Amazing work and description. Compared to this, my question is going to seem elementary BUT I couldn't resist asking considering the wisdom of the participants in this thread.

Basically, I have a airbag light on my dash in the fuel console area. It blinks, to full on, over the course of a few minutes after start up.

Someone, prior to me purchasing the car, cut the plugs (for what reason I don't know) between the seat and the wiring from the car. The plug on the car end is missing At this point all of the controls for the seat work. The heating in the seat work BUT am unsure how to rewire anything to do with the SRS concerning the seat. I am sure this is what is triggering the light.

I would be grateful for any suggestions, wiring diagrams, wire color charts or what you think will matter. Car is due for inspection on the first of May 2017 and I have done all I dare to do. I do NOT need an exploded air bag right now - or ever, lol.

 

These are GREAT places to start:

JaguarXK8ElectricalOBDIIcodes.htm

And:

JaguarTrainingGuides.htm