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<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DWPC:
There are lots of posts complaining about electrical and computer problems ending with "By the way, I also installed a ____ myself, and it was really easy."

The days of simply stripping a hot wire and adding electrical accessories are over. You've got to be pretty careful now. If the xenons draw significantly more current than the OEM lights, they might cause trouble with the computer in your H3 and affect unrelated things. Dealers are increasingly disallowing warranty coverage for electrical/electronics problems if they find non-dealer installed accessories. </div></BLOCKQUOTE>

If installed correctly and are a reliable certified brand, and I stress "correctly" and "reliable brand" there should be no interferrence caused that would screw up any of the onboard computers.
If installed incorrectly or they are an off-brand, non certified for EMI, then yes, they can screw up one of the on-board computers, or worse, toast the vehicle.
Even a large current draw should not mess up a computer, if installed correctly and the unit is tested. I real large current draw from one or many items could affect the generator, and that could give cause to a dealer to place a call to GM to see if the generator is still covered under warranty. (Dealers cannot void any part of a warranty issued by GM; only a GM representative can do that, since the dealer does not issue the warranty...been there done that.)

Just be careful of what brand is installed, and make sure to follow the manufacturers recommended procedures, and it helps to know if the procedure is correct.

When out in the field doing investigations I have seen vehicles that customers brought in for service or the vehicle is in the junk yard, where they have installed high current draw items (130 watt light for example) to wiring not designed for such a high current draw, and they are mad because GM won't cover the warranty or pay for the damages done.

I always recommend for any installation of any additional item (other than LEDs) to use a relay and wire directly to the battery, with a fuse right where the wire comes off the battery or junction block.