Proper welding procedures for electronics
find their way into the electronics.
The safest thing is to remove the
PCM from its connector. The issue is
not just with power; the chassis is
ground, any wierdness you create can
come in on a sensor wire, etc.
MIGs have 24V or so to throw and if
you stick the wire that's not dropped
in the arc anymore, but across the
workpiece, and not necessarily in a
short loop.
Keep the welder ground clamp close to
the work and use a bright-sanded patch
of metal. This minimizes voltage drop
in the return path. Start your arc from
the well-grounded piece, not on the
loose piece you're attaching, and travel
into the new piece. If possible, move
the ground clamp close to each different
weld bead point in turn.
...check your homeowners policy first...



