What cards are plugged into the motherboard?
What video do you have connected?
On 3 digit error codes, 4xx was monochrome video problems
Do you get any beeps?
Does it have a dipswitch (SW1)? What are the current settings of it?
With all cards removed, and SW1 (if it has one) switches 5 and 6 off, do
you get beeps?
Do you have any other 5160s available? (consider swapping BIOS ROM)