Nikon Coolpix P4 Troubleshooting
If the camera won't turn on the mostly likely cause is defective batteries. Make sure batteries are charged and the battery contacts are clean. The battery could possibly be dead; to verify this, test the battery with a voltmeter. If a voltmeter is not available there are certain distinct signs that indicate a dead or dying battery. If the battery holds its charge for only a short time or if the battery doesn't charge, it needs to be replaced. Nikon Coolpix P4 Battery Replacement
If the crack hinders normal operation, the screen must be replaced. Nikon Coolpix P4 LCD Screen Replacement
There may be loose or broke wires inside, this is more likely if the camera has been recently dropped or been treated roughly. Nikon Coolpix P4 LCD Screen Replacement
If the software is not working, the problem may lie in a bad motherboard, which would need to be replaced. Nikon Coolpix P4 Motherboard Replacement
When taking pictures, make sure press shutter button half way down to allow camera to focus properly.
Check to see if the camera lens appears grimy or has visible dirt on it. If needed wipe with a cotton swab doused in cleaning alcohol.
Go into the Menu, select Setup, then Reset All
Flash bulb may be burnt out, which would require replacement. Nikon Coolpix P4 Flash Bulb Replacement
Batteries may be critically low. Replace then turn camera on and off. Nikon Coolpix P4 Battery Replacement
Dust or other similar particles can block the lens from retracting. This may require professional help to remove.
If the lens is broken it will need to be replaced. Nikon Coolpix P4 Lens Replacement