Why is your service engine soon light blinking on your 2002 cadillac deville?

Answer 1

This is most likely because your Intake Plenum has a tear in it, you will need to replace upper intake gaskets and throttle body gasket (both can be purchased at Advance Auto Parts, or similar parts store, and your intake plenum which is a dealer only part, costs approximately $50 for the plenum, and $50 for the rest if you are doing it yourself it is a fairly simple job, you can check for this by spraying brake cleaner around the intake manifold and intake plenum gaskets with the engine running, if the engine rev's or stumbles this is your issue, the blinking SES light is due to un-metered air entering the system

You could also check your coolant level, a Northstar engine car is programed to switch to "Limp Home" mode when the coolant sensor senses a low coolant condition, which will also cause a SES light

If neither of these work please hold the "Info ^" button and the "ON/OFF" button for 30 seconds (until all segments on dash light up), then press "ON/OFF" twice (to select "All" then "All Codes") then write down all the codes that show with "Current" after them (Not "History" and post those for further help.