Cadillac Repair: engine diagnostic, cadillac deville, oxygen sensor

Question
hi,i drive a 1987 cadillac deville ht4100 4 door,i did a self diagnostic test and the codes e12,e13,e28,e59,e52,f41,f48 popped up,could you be able to explain what they mean and what to do about it,thanks

Answer
Hi Joe, If the car seems to run ok it could mean that someone was testing systems and set the codes and didn't clear them after they were done. I would clear all the codes and then diagnos whichever ones returned. A single E or F mean its a history code, EE or FF mean the problem is happening now.
E12: no distributor tach signal
E13: open oxygen sensor circuit
E28: open third or forth gear circuit in the trans
E59: VCC temp sensor circuit in the trans
F41: cooling fan fault
F48: low freon pressure switch problem

Hope that helps. Bill