Hello,

Check out this m15 R2 Service Manual System diagnostic lights.

It looks like that error is related to Power-rail failure. Without more research I couldn't tell you want that really means but it sounds like a bad system board.

You can try a power drain though.

Unplug the power adapter and battery (you'll have to remove the back panel) and then hold the power button down for 30-60 seconds.

Hi @DJBANGER   guess that m15 is not being powered by battery, and is powered by mains charger with m15 error code 3,5 Power-rail failure. The Power Supply Unit (PSU) provides different voltages to your m15 system and one or more of these different voltages is not available. Specific reason not known and this fault requires further investigation, usually by a qualified technician. Please ask your friend to tell you about this m15's problems and/or replacement parts history. 

If main battery can be charged on a different laptop, etc., it should be possible to boot your m15 system to determine if there are any other problems. Then click on Dell Support and allow it to detect your Service Tag. Then go to Drivers and Downloads and download the SupportAssist application into your local admin account, Run as administrator, then Restart. Run SupportAssist to detect and diagnose your m15 system. Click on troubleshoot tab to allow SupportAssist to troubleshoot your m15 system. 

I suggest you to follow the steps provided below, first to release any static power in the laptop that may be causing this issue:

1. Remove the battery and the AC Adapter from the laptop.
2. Press and hold the Power button for 20 seconds and release it.
3. Reconnect the battery, AC Adapter and press the Power button.
4. The laptop should power on if the static charge was the cause.

You can press the "Fn" key and the "Power" button to start the hardware diagnostics if the laptop fails to power on after following the steps provided above.

Please let me know about your findings.

Thanks for the information.

Hi @AdrianG001  please note earlier posts say m15 error code 3,5 is internal hardware PSU Power-rail failure. External ac charger is thereby prevented from providing the power requirements. Main battery has no power.