On board computers

Has anyone ever heard of damaging a vehicles' on board computer when tapping power from the ingition harness.  Is this possible?  A dealer tried telling me that some new models have what's called muliplex wiring, which when tapping into can damage the on board computer, but I thought the +12V supply on the ignition harnesses are straight power right from the battery.  This same person later told me that the vehicle was boosted because it had a dead battery, and that's how I think the on board computer got damaged.  Anycomments?

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inallalone

Yes if you tap into a multiplex wire incorrectly, regardless of where it is, you can damage the computer, ecu or bcm. If the truck was jumped by a tow truck then that probably is the problem.
Make them prove that the wire you tied into was infact multiplex. If they can't then tell them to go **** themselves.

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Certified Security Specialist
Always check info with a digital multimeter.
I promise to be good.
Tell Darwin I sent you.

I've been sick lately, sorry I won't be on much.

Thank you auex.  How can I check if it multiplex wiring?

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inallalone