Just bought another xj this weekend from auction and everything Seems fine besides won’t crank , said it’s was undercarriage damage so wanted to see if it possible have a inertia switch that could have got flipped

 

jayflymid, the XJ does not have an inertia switch. What it does have is if the car deploys the airbags, it triggers a relay to remove power to the fuel pump. This intern kills the car from starting. The only way to reset this is to get the SDD software and reset it inside that.

 

In addition to Thermo's excellent advice be aware that you might have a "permanent" code in your RCM (Restraints Control Module). This tripped by an impact and we have been told it is NOT erasable and the module must be replaced. This also brings up the complication of reprogramming the RCM to your car which will require the Jaguar diagnostic tools called SDD.

Do you have an operational SDD system? If not I would either get one or talk to my local Jaguar dealer to see if they can or will do the work.
One more hint we see an number of these crashed salvage cars come to auction. Most come with only one FOB/key. We have dozens of threads where people have only one key and then "something happens" and your now screwed. Get ahead of this and make sure you have two operational FOBS/Keys.
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the car didn’t deploy the air bags so could it still be the SDD software and it’s still getting fuel to the engine

 

Could it still be the RCM system if the air bags didn’t deploy, I’m gonna break down the whole front and see if the alternator or starter went out on it the reason for no crank

 

Until you get the car hooked up to SDD (Note with codes this deep it will be tough to find an aftermarket unit that can do all this?) We really don't know?
You need to understand throwing parts at it will be expensive and more importantly it just won't work.
These are massively complicated cars with everything connected to everything.

Is there anyway to get the car properly scanned with SDD? At least as a first step in the repairs?
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found a code reader I had put up a while ago but these are probably the only codes it can read don’t think it’s that high tech , these are the 3 codes that came across the scanner all where pending so I erased and only one popped back up was P0A0F

U0447
P0333
P0A0F

 

Hello jayfymid,

When you source vehicles from auction, i assume you have some DIY skils yourself?
The P0A0F code does mean "powertrain seizure detectd" and most likely when it is on, you don´t have crank by vehicles own starting circuit.
However, if you access the starter motor you can manually operate it by solenoid + wire. (engine might still not start)
I would first try if engine turns by hand tool from crankshft pulley nut. If not, remove the starter and check if there are starter driving gear failed and stuck against flywheel theets. Hopefully it is only this, because anything else are major work. From seized transaxle to failed transmission or totalled engine.
If i remember right from other marguee the P0A0F code can be only erased once the system detectes signals from sensors that the unit rotates again.
(Been pushing the vehicle about 5 meters after transmission change, before it let me erase the code and then it let me start from key)

 

Hey Vasara yes I have pretty decent DIY skills first jag I ever tried working on myself , usually I go for Toyota , Lexus , and Nissans and Chevrolet , the jag has a lot more going on under the hood and more systems so to me it was a lot more difficult cause I’m seeing a lot of grounds on the body and etc that could cause the slightest problem for power to crank wise and so you basically had to attach the car and roll it for the car to start that’s strange but I’ll check that out also

 

Yes post back as I hope you DON'T have a seized engine!
Note that the engine can only be turned in one direction without doing internal damage.
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