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I recently purchased a Hyundai Elantra Touring with the intention of towing a small trailer ( for a canoe and/or two adult and two children's bikes).  The Elantra Touring is advertised to have a 1500 lb tow rating.
The manual states, on page 4-42,"Use only an approved trailer wiring harness.  An authorized HYUNDAI dealer can assist you in installing the wiring harness".  When I asked my dealer for such help, I was told that there was no harness available and they could not help.   They suggested I contact a reputable hitch installer.  When I asked if there was any guarantee that doing so would not risk voiding my warranty, I was told no.
Not satisfied with this answer, I contacted Hyundai Consumer Affairs. They informed me that there was no approved harness available for US market vehicles.  They also stated that my warranty could be at risk if a trailer tow harness were to be installed.
Hyundai's famous warranty was a major reason for my purchase selection, along with the tow rating.  I had no idea that legally using the latter could jeopardize the former.  I find this somewhat deceptive.
Is this a common practice among manufacturers?