1984 Eldorado service soon message

[Billharrison]

I have a 1984 Eldorado with approximately 60,000 miles with a digital dash. A message light has come on saying service soon. When I checked the codes using diagnostics on the instrument panel it showed code #29. Does anyone have any experience with this issue ?

[TJ Hopland]

I'm not sure where my 84 manual is but from memory that is either an overdrive code or has to do with idle controls.    I think both of those are code 29 it just depends on the specific year make and model.