Check for polarity coming out of HU

[waxlrose]

Any sure fire way of testing polarity on the wires coming out of a head unit? I'm using my stock head unit and other than knowing the wire color codes is there any way to use say an oscilloscope or some other means of testing which wire is positive and which is negative?

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[fasfocus00 5,000+ posts]

DMM, continuity if you have visual access to the speaker. PT-9A will do the trick. I have a similar version of the PT-9A but it's millions of times easier and faster.