Cadillac Repair: 1994 Cadillac DeVille, cadillac deville, o2 sensor

Question
QUESTION: I have a 1994 Cadillac Deville 4.9 V8...a few weeks ago my computer came over telling me SERVICE VEHICLE SOON and my air bag light and ABS lights were flashing...i looked up the codes and I042(Battery Voltage too high), P016(Voltage out of range)(all SOL), and P091(PRNDL switch problem(transaxle range switch problem)...i drove around like that for about 1 1/2 days..and it turned off...and it's now back on telling me the exact same thing? What does this mean and what should i do?

ANSWER: You need to have the charging system tested to see WHY it is indicating over voltage. It could be most likely a faulty alternator, But testing it will tell you whether it is faulty or there is a computer problem.

P091 means that you have a fault in the NEUTRAL STARTER SAFETY SWITCH which mounts on the transmission.

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QUESTION: I did what you told me to do and got my alternator and battery checked..the guy at autozone said they are fine and that he thinks I might just have carbon built up on my EGR valve..and too take off my egr valve and spray it with carbon remover..I have also talked to more people who think its my o2 sensor because my friends moms car was doing the exact same thing my car is doing..do you have any ideas on what i should do since it's not the alternator?

Answer
If your fault was the alternator, You would have an oxygen sensor fault code from the computer. What you need to do is CLEAR (erase) all the codes from the computer via the climate control panel and see which codes return and watch to see which codes return as CURRENT or HISTORY codes and let me know. Once we get the codes fixed then you need to do a re-learn process to the computer.

NOTE: Removing the battery cables will NOT CLEAR the fault codes from the computer.