HP laptop wont boot up

[Henry764]

My Hp elitebook 840 g4 wouldn't boot up so tried the hold power button method didn't work opened it up to disconnect CMOS battery plus main battery plugged the power in and it booted took me to the post error for cmos battery where i hit enter to reboot it,then to post error again for second reboot it rebooted, post error again for the third time,after hitting reboot it completely shuts down.What could be the issue

[Samrit26]

Hello,

Possible Issues with HP EliteBook 840 G4 Boot

From your description, it sounds like your HP EliteBook 840 G4 is encountering POST errors related to the CMOS battery. Here are some potential causes and troubleshooting steps you can try:

1. CMOS Battery Issue:

   • Since the CMOS battery was disconnected, it may not be seated properly or it might need replacement. The POST error you are seeing could be due to a drained or improperly connected CMOS battery. Ensure that the CMOS battery is properly connected or replace it if necessary.

2. System Configuration Issue:

   • Clearing the CMOS can reset BIOS settings. Make sure to enter the BIOS setup and check your settings, especially the date, time, and boot order, as they may have been reset to default values that are incompatible with your existing system configuration.

3. Power Supply Issues:

   • Ensure that the main battery and the power adapter are working properly. Sometimes power issues can cause intermittent boot problems. Check all power connections and try a different power adapter if possible.

4. Hardware Connections:

   • After opening the laptop, ensure all connections, especially RAM modules, storage devices, and any other internal components are seated correctly. Loose connections can lead to POST errors.

5. POST Error Messages:

   • Pay attention to the specific codes or messages during POST as they can provide specific diagnostics information that can pinpoint the exact cause of the error.

6. Update BIOS:

   • If possible, ensure your system’s BIOS is up to date. Use another PC to download the latest BIOS update from the HP support site and update it using a USB flash drive.

7. External Peripherals:

   • Disconnect all external peripherals such as USB devices, external hard drives, etc., and try booting the system to see if any of these are causing the issue.

If after troubleshooting these steps your EliteBook still doesn't boot properly, it might require more detailed diagnostics or service by a professional technician.

Sources

1. HP EliteDesk 705 G3 Microtower Business PC - Maintenance and Service Guide