HP ZBook 15 G4 - Blinking Lights

2. Remove all external devices, including docking station. Recently added hardware
and/or applications may cause graphics driver conict and result in loss of video.
3. Perform hardware reset (8. Hard reset on page 89) and verify that HP Logo is presented
correctly on display screen when pressing F10.
4. Test with external monitor via VGA port (or DisplayPort, HDMI, etc). Press power button
and close the computer lid to force video output to external video. If unsuccessful,
contact HP service.
5. If external video is OK, update BIOS, software, and drivers (4. Update BIOS and drivers
on page 79) and perform soft reset (9. Soft reset (Default Settings) on page 90) if
needed. Go to next step to verify display.
Verify display
●
When booting to Windows, determine whether image appears on display screen (via
Windows Screen Solutions or Windows logo + P for display switcher).
●
If there is video on display, disconnect external display device, open the computer lid
and restart.
The sections below are intended for authorized service providers/technicians.
1. Verify Power Good lights are on to be sure that system board power is functional.
2. Reseat display cable connection on system board.
3. Reseat display cable connection on display panel side.
4. Examine and reseat major components, such as hard drive, memory.
5. Test with minimum conguration (11. Test with minimum conguration on page 91) by
removing hard drive to isolate operating system issues and testing video in F10 Setup.
6. If video is present, restart and retest the computer.
7. If video is present but bad, go to Display on page 113 section.
8. If issue persists (no video), test with external video.
9. If issue persists, test or replace a conrmed working display.
10. If issue persists, replace discrete graphics card.
11. If issue persists, replace system board due to defective video function.
Tips and tricks Swipe a metal piece (screwdriver) over wireless/mute buttons to act as if closing lid to force
video output to external display device. See the “External component identication –
Display” section for location of the magnetic sensor.
Blinking lights
Symptoms
Lights blink on keyboard caps
lock/num lock keys
Possible causes
Blinking lights on startup usually indicate a problem with basic functionality of a critical
component (processor, BIOS, graphics cards, memory, etc.) due to loose connection,
defective parts, or recently added parts.
Troubleshooting steps
1. Check for any blink patterns. Count the number of blinks in a sequence, followed by a
pause for a few seconds.
102 Chapter 6 Troubleshooting guide