The only diagnostic code that matters is when they stop blinking. So are you saying it ends with 1-2-3 on? And what color is the power button, and is it solid or blinking?
1-2-3 means "Another problem", and according to the manual:
- Ensure that all hard drive and CD/DVD cables are properly connected to the system board (see "System Board Components" on page 81).
- If there is an error message on your screen identifying a problem with a device (such as the floppy drive or hard drive), check the device to ensure that it is functioning properly.
- If the operating system is attempting to boot from a device (such as the floppy drive or hard drive), check system setup (see "System Setup" on page 127) to ensure the boot sequence is correct for the devices installed on your computer.
Check that the video cable between monitor and PC is connected correctly at both ends. Try a different monitor or test this monitor on another PC. Reseat the video card in its slot, etc.
Always power off, unplug and press/hold power button for ~15 sec before opening the case.
