Hi everyone,
Recently my mechanic changed wishbone and catalic converter, on 351 2012 xj 3.0
later the battery were were removed and boot was closed, he put the jump from front and I believe tried to put the ignition switch on, the boot opened but after this the car won’t start. Many intermittent codes came up but cant start the car. Your suggestion and knowledge will really be helpful.

 

Hi everyone,
Recently my mechanic changed wishbone and catalic converter, on 351 2012 xj 3.0
later the battery wire were removed and boot was closed, he put the jump from front and I believe tried to put the ignition switch on, the boot opened but after this the car won’t start. Many intermittent codes came up but cant start the car. Your suggestion and knowledge will really be helpful.

 

Assuming that the battery is now connected, and is adequately charged (very important), has it been disconnected again for a minute or so and then reconnected to force a reboot of all the car's modules in case they are crashed from a voltage drop if the jump source was inadequate? It probably has been tried already, but it is worth checking.

If that hasn't resolved it, what codes are being flagged up? Check for a common fuse on those circuits that may have carried too much current from the jump when ignition was turned on. I've checked the 2012 schematics and I'm not clear on which feed into the central junction/fuse box the stud for the backup power in the engine fuse box is connected to, but the BCM itself is protected by 2x 50A midis which suggests it is capable of a large current draw. It may be that stud is connected back directly to the battery fuse box, which distributes to the entire car rather than just the central junction box.

In the future, when disconnecting the battery always engage the trunk latch with a screwdriver shaft or similar to prevent it from being closed until the battery is reconnected again!

 

Ajaz, I would start with watching the instrument cluster as you attempt to start the car. IT is possible that the programming for the key has been corrupted and now the car is no longer seeing a valid key to start the car. The other thing I would look for is the inertia switch. You would need to reset that switch as that would kill the fuel pump and obviously, the car will not run at that point.

If these 2 things don't fix it, then I would say to clear the codes, attempt another start and see what codes pop up then. Post them here and hopefully we can make heads or tails out of those.

 

Thanks for replying
even my mechanic says that the programming of keys is corrupted, and to replace the KVM RFA. Is that possible just because the battery wire was not connected, it can stop the car from starting up, even when the engine is cranking.
can you plz guide me to exact location for inertia switch for 2012 xj LHS driver

 

Ajaz, there is no inertia switch per se for this car. You have a fuel pump relay which is activated by the ECM. The car senses a shock (accident), this relay gets power removed and kills power to the pump. So, I would say to start with looking at relay R3 and fuse F8 in the rear fuse box. Those are what control power to the fuel pump (aka, your "inertia switch"). You then have a driver module which is what actually controls the speed of the fuel pump and its output pressure. It does this by switching the fuel pump on and off at a really fast speed and by regulating the amount of on and off time, it acts as a variable voltage source. This module is located on the end of the vapor canister in the arch above the rear differential (on the end of the canister near the fuel fill line).

If these are not your problem, then I would say to first pull any codes that the car may have stored, that should tell you a lot about what the car is seeing and why it is doing what it is doing. Keep in mind, if say your fuel pressure sensor has failed, the ECM will not allow the engine to start as it cannot adequately regulate fuel pressure. There are tons of reasons why the car may not be starting. We need to figure out ways to eliminate things to narrow down the list of possible suspects.