I am guessing you have a GM. vehicle . Find the connector and there the two pins that are together at the end cross them with the paper clip with the key off then turn the key on the check engine lite will flash a code 12 . If it does not flash a code 12 you are not in the diagnostic mode and need to try again .
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I am guessing you have a GM. vehicle . Find the connector and there the two pins that are together at the end cross them with the paper clip with the key off then turn the key on the check engine lite will flash a code 12 . If it does not flash a code 12 you are not in the diagnostic mode and need to try again .