XPS 8940 not displaying and starting when plugin the power by itself

Question

Hello,

I am having a problem with my Dell XPS 8940. When I plug in the power adapter, the computer automatically powers on without pressing the power button. However, nothing is displayed on the monitor, and there is no response from either the mouse or the keyboard. When I attempt to force a shutdown by holding the power button for 10 seconds, the machine turns off but then restarts on its own after about 2 seconds, with the same problem persisting.

Additionally, the power button LED blinks in a pattern: two yellow flashes followed by three white flashes.

You can see this in the following video: https://drive.google.com/file/d/1ZyzKTuqnlH2C-9YjtrIRD8LkcKTockyI

I have already attempted to resolve the issue multiple times by resetting the BIOS through the removal of the CMOS battery and performing a battery flea discharge, but unfortunately, these steps did not resolve the problem.

For context, this PC has Ubuntu OS installed and is primarily used for CPU/GPU AI training. On several occasions, the machine has frozen during extended AI training sessions, causing no display or response while it was running normally. Each time, it required a forced shutdown, and it started up fine afterward when I pressed the power button.

The recent incident occurred after the system was functioning normally, but then there was a power outage. Since then, I have been experiencing this problem.

eyadgad · Accepted Answer

@eyadgad​  update: i tried using the DIMM 1 slot again, just to see if the problem persists. and it booted up normally

Chino de Oro · Answer

For the behavior you described, when plug in, Dell computers would perceived that power just restored from a power outage. It would turn on briefly to check power management settings in BIOS. If it was set as default to stay OFF, the PC then would power off. If the settings sets to resume power, it will stay ON.

For the LED error codes 2, 3, it indicates no memory detected. See the diagnostic light codes here https://www.dell.com/support/manuals/en-us/xps-8940-desktop/xps-8940-service-manual/system-diagnostic-lights?guid=guid-85db873b-6a6d-4609-b8b6-31ea6899c4b5&lang=en-us

If you have been disconnecting the PC from live circuit when not in use, the CMOS backup battery may have been depleted. Replace the coin cell battery with a fresh, new CR2032. Reseat the memory modules and perform a CMOS reset using the jumper. BIOS settings will need to be re-adjust to match hardware and usage preference.

If the issue is persisted, replace with known good memory module and test again.

ispalten · Answer

You have a couple of things going on here.

First one, you removed/replaced the motherboard battery. This would reset ALL settings. So I'd not worry about the XPS trying to boot when putting the A/C plug back on it.

Secondly, the power failure... and this can cause some errors.

If there was a spike before the power dropped, that alone could cause a problem like damaged h/w.
Depending WHAT was open at the time, some files could be corrupted, and a file needed for booting could be damaged and you'd be unable to boot.

You have 2 possible problems due to the led flashing:

One is that the BIOS settings being lost memory is not initialized.
The video card was damaged during a power spike.

The telltale there is no output on the monitor on an attempted boot.

You should have seen either the normal Dell Logo, or what I suspect would be the BIOS message that you needed to make some changes and it showed you to that settings need to be set?

You saw neither.

So, first thing first, the monitor, when on, can you see its MENU? If you can, then it probably is OK? If not, take it to another PC and see if it works.

Assuming it IS not the monitor, look at the h/w on the XPS.

If you have a DISCRETE video card, take it out, and connect the monitor to the Intel HD750 on the back of the XPS. See if you can boot or at least see the Dell log.

Still can't, since the LED's indicate a memory problem, take out all but one memory strip leaving the first one populated. See if you can boot.

Report back, but I can't think of anything else to try now?

RoHe · Answer

When testing RAM modules one at a time, use 2nd slot from CPU (DIMM1), not the 1st slot from CPU (DIMM3).

eyadgad · Answer

Thanks for help @Chino de Oro @RoHe @ispalten

I have only one 16GB memory card in DIMM 1. While attempting to fix the problem, I reinserted the memory card into the same slot (2nd slot, DIMM 1), but it wasn't seated properly, which caused the "no memory detected" error.

After properly seating the memory card, the problem persisted, but the LED blink code changed to 2,4, indicating a "Memory or Random-Access Memory (RAM) failure."

I then tried to move the memory card to another slot (3rd slot, DIMM 4), and the system booted up successfully.

I'm not entirely sure why, but the problem seems to be resolved. do you know why?

Also, It shouldn’t cause any problems or affect performance if the memory card remains in the 3rd slot, right?

bradthetechnut · Answer

@Chino de Oro​  ...'perform a CMOS reset using the jumper.' Just a reminder:  If your desktop computer was produced before April 2020, the computer most likely has a jumper-based reset. Desktop computers manufactured after April 2020 use the RTC Reset ability. In other words, pushing and holding the power button for 30 sec. resets BIOS.

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XPS 8940 not displaying and starting when plugin the power by itself

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