Cadillac Repair: timing, jumper wire, square boxes

Question
QUESTION: is there a plug that has to be unpluged inorder to adjust the timing properly on a 4.9 cadillac motor like u have to unplug the vacum advance on a older chavy motor

ANSWER: What YEAR & MODEL vehicle ?

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QUESTION: its a 1991 seville

Answer
With the engine at normal operating temp look under the dash near the steering column and you will see black plastic connector that has a black plastic cover on it. Pull the cover off and you will see letters M,L,K,J.H,G machine stamped into the plastic top row of little square boxes and on the bottom row you will see letters A,B,C,D.E.F stamped in the plastic connector.

You need to put a jumper wire and connect letter A to B in the connector in order to set the ignition timing.

Once you are done setting the timing, Remove the jumper wire and REPLACE the plastic cover.

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