HP t420 Troubleshooting Guide - Page 31

Interpreting POST Diagnostic Front Panel LEDs and Audible Codes

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Table B-1 Diagnostic Front Panel LEDs and Audible Codes (continued) Activity Beeps Possible Cause Recommended Action The heat sink/fan assembly is not properly attached to the processor. OR The unit has vents blocked or is in a location where the ambient temperature is too high. Red Power LED flashes four 4 times, once every second, followed by a two second pause. Beeps stop after fifth iteration but LEDs continue until problem is solved. Power failure (power supply 1. is overloaded). OR The incorrect external power supply adapter is being used on the unit. Check if a device is causing the problem by removing ALL attached devices. Power on the system. If the system enters the POST, then power off and replace one device at a time and repeat this procedure until failure occurs. Replace the device that is causing the failure. Continue adding devices one at a time to ensure all devices are functioning properly. 2. Replace the power supply. 3. Replace the system board. Red Power LED flashes five 5 times, once every second, followed by a two second pause. Beeps stop after fifth iteration but LEDs continue until problem is solved. Pre-video memory error. CAUTION: To avoid damage to the memory modules or the system board, you must unplug the computer power cord before attempting to reseat, install, or remove a memory module. 1. Reseat memory modules. 2. Replace memory modules one at a time to isolate the faulty module. 3. Replace third-party memory with HP memory. 4. Replace the system board. Red Power LED flashes six times, 6 once every second, followed by a two second pause. Beeps stop after fifth iteration but LEDs continue until problem is solved. Pre-video graphics error. For systems with a graphics card: 1. Reseat the graphics card. 2. Replace the graphics card. 3. Replace the system board. For systems with integrated graphics, replace the system board. Red Power LED flashes eight 8 times, once every second, followed by a two second pause. Beeps stop after fifth iteration but LEDs continue until problem is solved. Invalid ROM based on bad checksum. 1. Reflash the system ROM with the latest BIOS image using the BIOS Recovery procedure. 2. Replace the system board. System does not power on and LEDs are not flashing. None System unable to power on. Press and hold the power button for less than 4 seconds. If the hard drive LED turns white, the power button is working correctly. Try the following: 1. Remove the power cord from the computer. 2. Open the computer and press the yellow CMOS button on the system board for 4 seconds (located near the front USB ports). Interpreting POST Diagnostic Front Panel LEDs and Audible Codes 25

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Table B-1
Diagnostic Front Panel LEDs and Audible Codes (continued)
Activity
Beeps
Possible Cause
Recommended Action
The heat sink/fan assembly
is not properly attached to
the processor.
OR
The unit has vents blocked
or is in a location where the
ambient temperature is too
high.
Red Power LED
flashes
four
times, once every second,
followed by a two second pause.
Beeps stop after
fifth
iteration
but LEDs continue until problem
is solved.
4
Power failure (power supply
is overloaded).
OR
The incorrect external
power supply adapter is
being used on the unit.
1.
Check if a device is causing the problem by
removing ALL attached devices. Power on the
system. If the system enters the POST, then
power
off
and replace one device at a time and
repeat this procedure until failure occurs.
Replace the device that is causing the failure.
Continue adding devices one at a time to
ensure all devices are functioning properly.
2.
Replace the power supply.
3.
Replace the system board.
Red Power LED
flashes
five
times, once every second,
followed by a two second pause.
Beeps stop after
fifth
iteration
but LEDs continue until problem
is solved.
5
Pre-video memory error.
CAUTION:
To avoid damage to the memory
modules or the system board, you must unplug the
computer power cord before attempting to reseat,
install, or remove a memory module.
1.
Reseat memory modules.
2.
Replace memory modules one at a time to
isolate the faulty module.
3.
Replace third-party memory with HP memory.
4.
Replace the system board.
Red Power LED
flashes
six times,
once every second, followed by a
two second pause. Beeps stop
after
fifth
iteration but LEDs
continue until problem is solved.
6
Pre-video graphics error.
For systems with a graphics card:
1.
Reseat the graphics card.
2.
Replace the graphics card.
3.
Replace the system board.
For systems with integrated graphics, replace the
system board.
Red Power LED
flashes
eight
times, once every second,
followed by a two second pause.
Beeps stop after
fifth
iteration
but LEDs continue until problem
is solved.
8
Invalid ROM based on bad
checksum.
1.
Reflash
the system ROM with the latest BIOS
image using the BIOS Recovery procedure.
2.
Replace the system board.
System does not power on and
LEDs are not
flashing.
None
System unable to power on.
Press and hold the power button for less than 4
seconds. If the hard drive LED turns white, the power
button is working correctly. Try the following:
1.
Remove the power cord from the computer.
2.
Open the computer and press the yellow CMOS
button on the system board for 4 seconds
(located near the front USB ports).
Interpreting POST Diagnostic Front Panel LEDs and Audible Codes
25