Cadillac Repair: serv engine soon, service engine soon light, code letters

Question
1990 Fleetwood Cadi 4.5 V8. It has org. wires - plugs were replaced 4 yrs. ago.  Cars has been running smooth up until now.
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Followup To

Question -
Car has 100000 miles on it has been running great.  Today it was runing a little rough.  The service engine soon light has been comming on about twice a week and then goes out right away.  Do you have any suggestions?  Thanks Greg

Answer -
YEAR and MODEL ?.  

Answer
1. Ignition ON, Engine OFF.

2. Simultaneously push and hold the OFF and WARMER buttons until the whole display illuminates and release the buttons.

3. Code LETTERs/NUMBERS will start to appear, Write them down in the EXACT order in which they display and how many times they display. until it stops at .7.0


Let me know the codes.


If you lose track, Turn OFF ignition and start over.