Hello everyone, I’ve been reading the posts on this fourm for a while and it's been filled with helpful information. I’ve got a 2012 XJ supercharged that I am having a problem were it won’t start now after replacing the rear brakes. It all started with a rear brake pad replacement that turn in to replacing the calipers after one was frozen and wouldn’t retract. After replacing the calipers and bleeding the system the car would not start. It had been giving a low battery warning for a few weeks prior so I went ahead and replaced the battery. The car still would not start after the battery replacement. It has power, the dash lights up but nothing happens when pressing the start button other then a single click that sounds like it is coming from the rear of the vehicle. Verified that the key was being detected, when key was moved away the key was not detected message appears on the dash.. Have tried turning the ignition on and then pressing the break and hitting the start button again still no luck. Tried starting it, getting out locking the car, getting back in and starting like I seen suggested in another post I have seen and again nothing. Has anyone else encountered similar behavior or have any ideas?

 

You may have to press really hard on the brake pedal for it to register.

 

mds004,

I would do as XJ8JR suggests, if than doesn't work it 'may' be your brake light switch.

The brake light switch (Ford part) contains two switches within the same body. You need to activate BOTH switches for the car to start, but only ONE to activate the actual brake lights and ACC cancel etc.

So, standing on the brake pedal, while trying to start the car may be enough to activate both switches.

wombat

 

This. I would start with this. I'm always shocked at how hard I have to press the brake on my 2011 to get it to start.

 

First, make sure that your battery is fully charged. Use a 10 Amp or greater battery charger or battery maintainer, not a trickle charger.

Then press the START button FIRST and hold it in before you step on the brake pedal (Yes, I know the Owner's Handbook says to step on the brake pedal first.).

If it doesn't start as soon as you step on the brake pedal, you might have to step on that pedal with both feet and all your strength while pressing the START button.

Good luck!

 

Just had the exact same problem, even just had a brake job back in June. Car had power, battery new, just like yours. At startup nothing, no crank, no turnover, dead. Yet everything had power and new battery. There was a main power cable from battery to front under hood junction box that was corroded somewhere in the middle of the car. Took my jag guy a day to figure it out. It made everything as you describe except upon on hitting the start button no power to start. New cable was priced at $1K through Jag. My guy soldered it, repaired it. Still cost me $600 with diagnostic time and repair. Hope this helps.

 

That was a good repair and glad he found it!
Surprised he did.

Of course no idea what brakes had to do with it?
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Brakes had nothing to do with it. However, when I ran across this thread I was having the exact same problem after having my rear brakes re-done. Car would not turn over or start but clearly had power on a new battery. This thread made me think about brake light switch as to the reason it was not starting. I took it back to the shop questioning some issue with the rear brakes, brake light switch, etc. I, as well as the tech, were expecting some related issue. Brakes were really just conincidental to the problem which was a short. The short allowed everything to appear normal power wise except it would not allow enough power to engage the starter, etc. Point being his brakes may just be coincidental to another issue. Sometimes hoof beats really do mean Zebras.....

 

Thank you everyone for the replies and suggestions. This evening I was able to resolve it and got the car to start again. On a whim I decided to re-bleed all the brakes again to see if that had any impact. After going through the bleeding procedure the car started right back up as normal. There was still a little bit of air in the passenger rear side that took a little bit of work to get out.