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Cadillac Repair/1990 cadilallac Brougham, service engine soon light

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Expert: - 8/15/2010


Question
I have a 1990 Cadilllac Brougham rear wheel drive with the 5.7 engine with  fuel injection. When I first start and drive the car no service light problem.  After I drive the car about 3 to 5 miles the ( service engine soon light ) comes on. The car still runs fine and does not seem to bother performance of car. Any suggestions on what to check?   Thanks

Answer
Hello,

This is an emissions problem and no, your engine is not running to full efficiency. This light is a symptom and until diagnosed with a code scanner (available at parts stores), the problem will not be known. The light comes on to store a trouble code with the computer system. Just because that light is not on all the time does not mean there are not codes stored.

In fact, if the light stays on, that tells you it is a hard code and something needs fixed right now.

If my answer assisted you, please rate it.

Thanks,

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Rob Painter

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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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