So you think that wire is either constant 12v or ignition 12v then?

Is it safe just to run an extra wire to battery or ignition and see if that works? I see no way of finding out where that blue wire goes since its part of the harness and I'd have to tear the intake manifold apart to see where it went...

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k