Starter problem ls 400

Try shifting the gear selector into neutral , if an automatic transmission . If it is a standard shift,the clutch pedal switch may be malfunctioning

if the battery is all right, the starter or igniton have a problem.
obd2 tools

The starter itself might need cleaning of old dirt, grease, oil, or crud inside, but I think your starter solenoid is failing. The contacts in it are probably pitted and failing.
Those starters are pretty bullet-proof. Don't exchange it for a cheap alternative. Just replace or repair the solenoid.

this could be many problems. 1 battery 2 the starter if the engine clicks when u turn the key u have a dead battery. if it does not click and still does not turn over even after u tried to charge the battery then u have a bad starter.

your battery isn't fully charged, or your battery contacts need to checked/cleaned!! The starter isn't getting enough power, this is the reason for the slow spin and clicks.

probable starter motor
if you can get at it have someone turn key to start and tap on starter with something it may start. it also proves a bad starter

Yes your right its the soleniod, might need the wires cleaning up that connect to the starter motor sometimes they go rusty so the connection is not good enough, worth cleaning before you replace it.

CHECK THE IGNITION SWITCH FUSE.IF IT LOOK OKAY.I AM LOOKING AT THE IGNITION SWITCH.IT COULD BE OPEN.ITS NOT SENDING POWER TO STARTER.

There are a number of things that could cause that. Try turning the key to the on position and crossing the starter terminals with a screwdriver. If it starts you have a bad ignition. If it still just clicks your starter has seized up or your battery might be lacking the charge to do the job. Hope these help you.

Anti-Deterrent ECU:
This is also possibility especially someone else drive your car. This is very common if you lend your car to someone. The symptom of this condition is "No noise or sound at all" when ignition key is turned. If this is faulty, the symptom will be the complete ignition kill. Therefore, you will not heard and clicking sound or engine turning at all. If this is the problem, you can easily reset the Anti-Deterrent by using your key. Stand out side of the car and close all doors. Insert the key into the driver side door and turn the key to clockwise and counterclockwise for three four cycles. Basically, you are lock, unlock for 4 times and this procedure will reset the anti-deterrent ECU. If this happen to you, its quite scary at first, but the solution is very simple.