95 S420 Fault Codes

[normwm]

All:
My 1995 S420 check engine light cane on at about 79,000 miles. This car has a button and a red LED under the hood. I pressed it for 3 seconds and read the number of blinks, getting 3 codes.
Since no service manual is available (either on paper or CD) how do I find out what the fault is?

Is a service manual available for this car?

Thanks