Hmmm...According to my shop manual, code 58 is for the "Pass Key II fuel enable circuit."
My '92 SSE supercharged has this code stored most of the time since I've owned it, but as far as I know it has never triggered the SES light or caused any driveability problems.
The "Pass Key II" functionality has to do with the factory security system.
I think I remember reading a technical service bulletin that said this happens on some '92 vehicles and isn't a problem unless there are other symptoms, because as long as this code has been stored for a while the system still allows fuel and ignition.
'99 Bonneville SLE, white, 112,000 miles
'02 Park Avenue Ultra, white diamond pearl, 88,000 miles