A little 9V battery should be fine. Try it and see if you get any "clicking" when applying it to it. I don't think you need to hack up your harness tho, just a little creativity.

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2003 BMW X5 3.0i -- MT5, 3.64s final gears, H&R lowering springs, K-Mac bushing kit
2007 BMW X3 3.0Si -- MT6