Re: Dell precision 490 workstation does not start anymore
If 1 & 3 are flashing (along with the power button flashing amber) it means the PSU has an issue.
If 1 & 3 are solid (and the power button solid green) it points to a memory error. If it's a memory issue, try disconnecting then reconnecting the memory sticks. If that doesn't help, try each memory stick, one at a time in each slot to see if you can narrow it down to one stick or one slot.