What is the Power Supply Unit (PSU) built-in self test (BIST)?

Dell Inspiron, XPS, OptiPlex, Precision and Vostro desktop systems include a power supply with a built in self-test (BIST) feature that helps diagnose the health of the power supply unit. The LED indicator on the PSU helps identify if the power issue is caused by the power supply unit.

 Note: Certain older models of Dell Inspiron, XPS, and Vostro desktop systems may not be equipped with a PSU built-in self test. To troubleshoot power issues, see the Dell knowledge base article How to Troubleshoot Power Issues on Dell Desktop or All-in-One Computers.

How to identify if my Dell desktop computer has the PSU BIST?

The PSU BIST is found on the back panel of the desktop computer, next to the power cable connector (on some smaller chassis types, you may need to remove the system cover to see the BIST on the side of the PSU).

PSU BIST with a test button
PSU BIST without a test button

How to use the BIST to diagnose power supply issue?

How to run self-test using the button on the PSU

1. Turn off the system.
2. Press the BIST button on the system and check whether the LED lights up.
3. The light should be solid on not flickering or flashing and the power supply fan should also turn on to speed. If the fan is not spinning up properly this should be considered a BIST failure even if the LED lights up.

• If the BIST LED lights up, then the power supply can deliver power to the system but something else is impeding the POST process. The next step is to check whether the power button might be at fault. If it is, not you should go to the following article for No POST troubleshooting.
• If the BIST LED does not light up or the PSU fan does not spin correctly, then the power supply cannott deliver power to the system and could be caused by any component connected to the power supply or the power supply itself. The next step would be to isolate the source of the power failure by disconnecting parts from the PSU, you should go to the following article for No Power troubleshooting.
  • Resolve No Power, No POST, No Boot or No Video issues with your Dell Computer.

How to run self-test without the button on the PSU

1. Turn off the system.
2. Disconnect the power cord from the PSU, and wait for 15 seconds.
3. After 15 seconds, connect the power cord back to the PSU.
4. The LED light should stay on for 3 seconds and then turn off.

• If the BIST LED lights up, then the power supply can deliver power to the system but something else is impeding the POST process. The next step is to check whether the power button might be at fault. If it's not you should go to the following article for No POST troubleshooting.
• If the BIST LED does not light up, then the power supply can't deliver power to the system and could be caused by any component connected to the power supply or the power supply itself. The next step would be to isolate the source of the power failure by disconnecting parts from the PSU, you should go to the following article for No Power troubleshooting.
  • Resolve No Power, No POST, No Boot or No Video issues with your Dell Computer.