Article Summary: OptiPlex 790 and 990 May Experience Intermittent No POST
OptiPlex 790 and 990 May Experience Intermittent No POST with 2-3-4 Error Code
Some OptiPlex 790 and 990 users are reporting that their systems will not intermittently not power on. The diagnostic error LED’s on the front of the system will produce a flashing 2-3-4 error code.
Removing power from the system for approximately 30-60 seconds to drain excess (flea) power, and plugging the system back in will temporarily cause the system to POST again. The first POST will produce the following errors.
- Air Temperature Sensor not detected
- CPU 0 Fan Failure
- Hard Drive Fan Failure
- Keyboard Initialization Failure
After this error, the system will perform normally until the intermittent No POST symptoms return.
Update the BIOS
To update the BIOS to the latest version
Note: Before updating the BIOS of your computer, ensure that the battery is charged to atleast 10% and connect the AC Adapter.
Do not turn off your computer while updating the BIOS/Firmware or you may harm your computer. During the update, your computer will restart and you will briefly see a black screen.
Disconnect all external devices that are connected to your computer.
Save all the files or documents that are open before proceeding with the BIOS update.
- Browse to the Dell Support website.
- Select your Dell Product using one of the following methods:
- Click Detect Product. This will install the Dell System Detect application on your computer which will automatically identify your Dell computer.
- Enter the Service Tag or Express Service Code of your Dell computer and click Submit.
- Click on View Products and manually select your Dell computer from the list of options.
- On the Product Support page, Click the Drivers & Downloads tab on the left pane.
- On the right side, ensure that the correct Windows Operating System is selected. If not, click Change OS and select the correct Operating System installed on your Dell computer.
- From the list of driver categories, click on BIOS to expand the menu.
- You will find the latest BIOS Update file listed. Click on Download File to start downloading the file to your computer.
- Click Save on the download prompt.
- Go to the location where the file was downloaded.
- Right-click on the downloaded BIOS Update executable file and click Run as Administrator.
- If you notice a prompt from User Account Control, click Yes.
- Click Yes on the BIOS Update Program window.
- Follow the on-screen instructions to complete the BIOS Update. Your computer may restart a few times to complete the BIOS Update procedure.