I think I would spend the extra bucks to keep the trailer isolated from that
$500 lighting module.

I have a 1998 Taurus with 3.0 engine I'm putting a trailer hitch on.
When I went to buy the wiring adaptor to add the trailer plug to the
Taurus I was quoted a price of $69 for the wiring kit. The parts store
said it was so expensive because of a computer isolation module. After
some research I found the difference, the expensive kit has two  wires
that run all the way to the battery and draws power directly from the
battery, the module keeps the trailer wiring seperate from the car. I
checked with another parts store and they wanted $75 for the kit. Of
course both warned of dire consequences & damage to my car's computer
if I didn't buy the expensive kit ( the only one they sell).  I
searched the net and found other kits for the 98 Taurus, one from JC
Whitney, for $20-30 that plug right into my cars wiring plugs ( very
neat looking) without the isolation module.  My question is what could
happen if I use the cheaper kit? Is the computer that sensitive? or
will I just get a"tail light out"  warning or something like that. It
would seem that other people are buying the cheap kit without
problems. I don't want to shell out the extra cash unless it's really
necessary.

TIA

Frank