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Cadillac Repair/91 Cadillac Seville- Service Engine Soon Light

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Expert: - 12/3/2011


Question
Hi Rob,

I just purchased a 91 Cadillac Seville and I have to get an inspection sticker with in the next 4 days. To me, the car seems to be running fine however, on my way into work this morning my service engine soon light can on. Any ideas?

The codes are:

E048 HISTORY
B120 HISTORY
B121 CURRANT
B448 HISTORY
B450 HISTORY
B552 HISTORY
NO SIR CODES
?ECM

Thank you!

Answer
Hello,

I don't have any service manuals dating back that far so I cannot assist you with the codes and if you are under that 4 day time line, you will need to take the vehicle into a service garage (not a dealer) that has diagnostic equipment for the old OBD (on board diagnostics) system. in 1994 GM went to the newer world wide standardized system OBD II.
Most larger service centers have this equipment and can determine exactly what the problem(s) are. The codes are only a symptom. One problem can set off a number of codes in the history. When it says EO48 History, it means that what ever EO48 is, was set off as a soft code indicating there was a problem in that system, but the service engine light did not stay on permanently and was ignored. The service engine soon light not going out tells you there is a hard code and something that has to be serviced now.
A loose gas cap can set off a variety of codes to give you an idea of the sensitivity.
Let's say you have a code 13 and a code 34. The code 13 O2 sensor will cause a code 34 map sensor fault as well. So, you may have only one problem that cascades itself.
Unfortunately, in it's current state, it will not pass an emissions test and without the proper diagnostic equipment and knowing what the codes mean, this is not something you can correct yourself.
With the service engine soon light on, you will not get the optimum mileage and power out of the car either.
There is no way to estimate a cost for repair without knowing what sensor or connection is bad, or if the ECM (computer) is bad and you will know all that when a proper diagnostic test is performed.

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Rob Painter

Expertise

Alarm system questions cannot be answered on this forum. These systems are not what I can answer. Without being physically at the vehicle and not knowing what kind of electrical service has been done on the vehicle, there is no possible way to give an accurate answer over the internet. My expertise is in Ignition/key based anti-theft systems. These issues include GM VATS (resistor chip in key blade) PASSLOCK (MRD)-ignition lock rotation based, no special ignition key and the PKIII Transponder (computer chip in key) systems. These systems are not alarm based and are integral with the starting of the engine. This is why I cannot diagnose alarm problems without physically looking at the vehicle: Alarm systems are a completely different annimal than ignition key/lock based anti-theft system. Many alarm questions come from vehicles 10 years old, and since older, many hands that had been involved over the years.I am an expert in all GM factory (ignition/key based)systems. Alarm system questions pose to many situations beyond my knowledge as to what has been done to the vehicle over the years. Some guy may have actually wired the stereo into the alarm system. Who knows? Over my past 30 years in vehicle wiring repair, I have seen unbelievable wiring disaters done by guys that consider themselves "mechanics." I have seen stereos and alarms intalled using surgical tape. I have seen modules burn up, un-fused circuits, wiring jambed between the doors and even lamp cord used for a starter kill. To answer alarm questions over the internet without examining the vehicle is like asking; What does it take to remove a dent?

Experience

Education/Credentials-ASE certified. 11 years with a GM dealer and 17 years with a repair facility dealing with only the repair of theft recovered vehicles.

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