2004 xk8 inertia switch, how to reset?

There's a relay in the under hood fuse block, look for the starter relay then hold a finger on the relay while someone turns the switch to start if it clicks remove the relay and with a 14 gauge or larger piece of wire jumper terminals 30 to 87 if the engine cranks replace the relay if no start replace the starter. If the relay doesn't click check the transmission range switch connectors, there may also fuse marked "start".
I hope this helps. Take Care.

You are saying that the starter motor is not working, that the engine is not cranking over, even with a boost?

If so, then either there is a problem in the starting circuit between the ignition switch and the starter, or the starter is bad. There is a way to check the starter on the vehicle: the starter will have 2 electrical connections. One is the positive battery cable, and the other is a small wire connection to the starter solenoid, mounted on the starter. The key should be off, the brake set, and the transmission in park or neutral. Use a small jumper wire or a small screwdriver, and jump the battery cable connection to the solenoid connector. Take off the solenoid electrical connector if you need room to do this. With key off, the engine won't fire and run, but if the starter is good, then jumping those two connections will make the starter engage and spin the engine over. (Of course, if key is in ON, the engine should start and run.) But you are just checking starter operation, so keep the key off. If starter is good it will crank the engine over. If jumping the two connections causes nothing, then it is pretty certain the starter motor or the solenoid is bad, and you need to replace it. (Take off the negative battery cable from the battery first to remove the starter from the vehicle.)

If jumping the starter caused it to operate, the starter and solenoid are good, and there is, again, a problem in the start circuit from the ignition switch to the starter solenoid. It could be simple like an electrical connection (like the one right there on the solenoid), or a component in the circuit between the ignition switch and the starter solenoid, like the neutral safety switch for example. You will need a wiring diagram and a multi-meter to diagnose further. Good luck, and hope you find the problem. Are you sure your battery is still charged up good?

This should be in the owner's manual. I found the below on autozone.com, their repair help location:
An inertia switch is used as a safety device in the fuel system. The inertia switch is located in the cab, generally under the dashboard on the right side. It is designed to open the fuel pump power circuit in the event of a collision. The switch is reset by pushing each of 2 buttons on the switch simultaneously (some models use switches with only one reset button). The inertia switch should not be reset until the fuel system has been inspected for damage or leaks.
When the ignition switch is ON , it turns the EEC power relay ON . The EEC power relay provides power to the powertrain control module (PCM) and the control side of the fuel pump relay. Power for the fuel pump(s) is supplied through a fuse link or high current fuse attached to the starter solenoid (battery side). From the fuse link or high current fuse, current flows through the fuel pump relay and inertia switch to the fuel pump(s). The fuel pump relay is controlled by the PCM.
When the ignition switch is turned ON , the fuel pump(s) will operate. If the ignition switch is not turned to the START position the PCM will shut the fuel pump(s) OFF after 1 second. The PCM will operate the fuel pump(s) operate the fuel pump(s) when the ignition switch is turn to START position to provide fuel while cranking.
After the engine starts, the PCM will continue to operate the fuel pump(s) unless the engine stops, drops below 120 rpm or the inertia switch is tripped.

The most frequent problem is the Inertia sensor if the engine cranks, but will not start. This switch is usually behind the floor kick panels and has a Reset button on it. It's purpose is kill the power to the fuel pump in the event of a collision. But sometimes slamming a door or trunklid will trigger it.
If the engine does not crank, check the brake lever switch. It can get broken or displaced by the Drivers feet. If the signal from this switch is missing, the brake lights won't work and the starter may not work.

Try resetting the Inertia switch for the fuelpump. On the drivers side, by the side above the carpet there is a kick panel. Remove the panel and press the button on the switch you see there. This will reactivate the fuelpump. This will work if the engine cranks.

If the engine does not crank, check the operation of the brakelights. If the brake lights do not work, some automakers will prevent the engine from cranking by locking out the starter. Others will set it up to allow the engine to start and not go into gear.

For this brake related problem, there is a switch on the brake pedal lever which may have been kicked by feet and is either broken or out of adjustment. The engine will crank if it did not crank before once this switch is worked on.

Hello! When you say does not start; Does the starter motor crank?...If the starter motor cranks the engine the anti-theft is clear...If such is the case, lets eliminate the Inertia Fuel Shut-off Switch...The inertia fuel shutoff switch is located on the LH side lower back panel in the luggage compartment and is manually reset...To reset the inertia fuel shutoff switch; press button on top...Send a comment...Guru...saailer

I’m happy to help further over the phone at https://www.6ya.com/expert/david_6df67de3b14de867

Does the car crank with the new starter? If it does, then it might be fuel system or ignition system problem. Take one spark plug wire off, put a screwdriver in the wire and rest it near a metal object on the engine. Have someone crank the car while you watch for a spark jumping from the screwdriver to the engine. If so, then the problem is fuel related. Don't touch or hold the screwdriver while cranking, it will be shocking. Some ignition systems can stop your heart.

Hello, you need to determine if its fuel or ignition problem

take a screwdriver pull off one of your spark plug wires at the plug and place the screwdriver in the boot hold it about 10 mm from the engine block and be sure to hold the handle back at the end have a friend spin it over if there is no spark you may have a bad crank sensor or coil pack

does the engine sound normal when cranked? if it sounds weak or spins faster than normal you may have a broken timing belt

there is a access valve on the fuel rail so you can check the fuel pressure if you have an appreciate gauge

do you hear the fuel pump run when you turn the key to the run position ? It will only run for a couple of seconds

if you don't hear the pump run try resetting the inertia switch Check your owners manual for the location

Thanks

Turn over manually? Is this jumping the starter with a wire or screwdriver to crank the engine or turning the engine with a wrench?