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Cadillac Repair/90 deville 4 door check engine light is on

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Expert: - 12/23/2010


Question
hello,

The check engine light is on after i put in gas ? I was thinking i was putting in the wrong gas so i uped it to 91 octane premium. the light went off after driving for a while then came back on . The car runs fine. Just when I get gas it comes on then off again and sometimes it stays on for weeks . I read your other replies so i tried the check engine test and this is what came up : 8.8.8 E48 E52 .E.E E48 .7.0  then i pushed the econ button then F.8.5 came up  . can you please help me? .....

Answer
Hello,

I have no such replies. It has been far too long since I worked with that computer system to accurately tell you how to get the diagnostic codes. The system was changed in 1994 to the OBD II standard which is completely different in a 1990 GM vehicle. All I remember is to cross two wires on the computer port under the dash and the code would be displayed by the number of flashes in the check engine light. If the light stayed on and then blinked 4 times that would be a code 14. Then one would need to see what code 14 was in the service manual and then the diagnostic and repair process could be engine.

Your car will run great until the emissions light (check engine) light illuminates. At that time it is not running in what is known as closed loop and the engine will get bad gas mileage while emitting emissions.
As for the terminals to be crossed, I no longer remember, but a local service center may be able to assist you.


This system has not been used since 1993.

Good luck!

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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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