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If the wires have the same color code, they more than likely connect together. If they do not have the same color code, I wouldn't do it. Connecting wires together without knowing the source and destination is asking for trouble.
A test light has no voltage/amperage, so it can't "over amp" anything. Auto computers are well protected, and are not that delicate anyway.
I have been in the electronic field for over 40 years, I do auto wiring, trailer wiring, and diagnostics as income since my retirement. jd