My 2012 Jaguar XJ, the warning light of airbag was on recently. My garage asked me to replace the long airbag on the top door panel of the left front and back door. After change, the warning light was still on. I was then requested to replace the airbag computer module additionally.


I have some questions to seek your advice:-
1) Some people told me that for some expensive car, like Mercedes, BMW, if there's something wrong with the airbag, there's some parts within the gearbox or brake that would hold the car speed to a low limit, so that one should bring the car for inspection asap..
If there's something like this with the Jaguar, why it was not working?


2) If jaguar doesn't have this function, shouldn't the garage determine to check if the computer module was malfunction first, instead of replacing the airbag right the way?


Thank you for your advice.
FP

 

FPong, the "low speed safety function" that you refer to is more for the power train, not for the airbag system. You will see some message to the effect of "performance limited" or the like which will normally limit the engine RPM to 3000 RPM. This will allow you to drive out of the situation, but keep the engine parameters hopefully in a range that it will not cause further damage. This is where noting the check engine light status (on solid or flashing) will tell you a lot. On solid means that something isn't right, but things should not cause further engine damage. IF the light is flashing, that is telling you that current conditions have a high probability of causing engine or related component damage. In some cases, you can get the restricted performance with a solid light on if you have a bad vacuum leak for example.

As for why they replaced what they did and the order, this is a hard one to answer. Being someone that works on electronics like what are in vehicles, there are a lot of factors that play into this. If you are following what the book says, when you get a code from the computer, it will say to replace PART A first, if the problem continues, then replace PART B, if it continues...... So, you may possibly end up replacing 3 or 4 things before you get to the actual bad component. This is where a knowledgeable tech can be worth a lot since he may know that replacing the first 3 parts hardly ever fixes the issue and replacing PART D does. He will skip the first few parts and jump right to PART D.

If you were to get the code that they pulled, it will say something to the effect of "driver's side airbag system open/short condition noted". Ok, what does that mean? Is the airbag bad, did the computer have a failure and now senses itself being bad, did you damage the wiring between the computer and the air bag, ....... This is based on a very simple system. You start getting into things like the engine management system, you may have 5 or more sensors all working together to control 1 parameter. This is where noting all the associated codes can help narrow things down in that case.

 

Thank you Thermo for your in depth advice.


It seems the garage lacks of the expertise to deal with this kind of tricky problem.


I have the replaced airbag in hand, is there any way that I can check if it is still usable in a good condition?


Don't know if I am that unlucky to have this Jaguar with so many other problems too! Besides this replacing of the airbag, I had and still having problem with the sunroof, with the door handle, with the glovebox lock, with the "Oxidized" door chromes, and most annoying of all, with the melting of the plastic surface of most of the buttons on the steering wheel, dashboard and doors, which is so sticky and cannot be cleaned away.


regards
fp

 

FP, DO NOT!!!!!!!!!! use a multimeter to test the air bag. It is possible that you can activate the air bag with a multimeter, resulting in the airbag essentially exploding in your face, resulting in an injury. They make special testers for airbags. Unfortunately, there is no test that you can do to see if the airbag is good. I wish I had better news, but that is the short of the story.

As for your other problems, I am new to the XJ too and am still learning all the quirks of the car and potential fixes.

 

Thank you, Thermo.
I dare not to test the airbag, don't worry.


fp

 

Is there anybody please give me advice as to how to
1) clean the oxidized chrome
2) clean the sticky plastic buttons.


Thank you.
fp