This is a complicated subject. Every travel club and Mexican insurance company has information that is either old or incorrect. They never offer a link to the Mexican Gov. Sonora is a special case. At one time we could get a Sonora Only permit for our vehicles instead of a TIP. Then they decided that no permits would be required in that Northern Sonora area. I think they were having problems with Mexicans and Gringos bringing in RV's and quads and leaving them here. Soon there were complaints from quad dealers in HMO. For a few weeks it was chaos at km21 ( Nogales). RV'rs heading to Sab Carlos or Kino were told that even though this was no hassle zone they would have to disconnect their toads or get permits . But each Aduanero was interpreting the rule differently. But it all got straightened out.The explanation the fellow at Nogales gave me is: Cars and Trucks can enter this zone with no permit. They are considered vehicles. However motorhomes are not considered vehicles in this instance ( go figure/. They are RV's and need a 10 year TIP. I called Sonora Tourism in HMO and she gave me the contact # in Nogales. He was not some ordinary Aduanero. He totally understood my question and spit out the answer with the explanation. The only place to get the correct answer is either Nogales or Mexico City. I refuse to call Mexico City as it is a phone bank with so much noise it is impossible to understand. At km 21 there is a booth near the Banjercito with a sort of ombudsman. The sign says he can help with Banjercito problems as well as SAT. When one of the Banjercito persons has a problem they send you to that booth. He will either help you with proper information or tell you your problem is not solvable and your vehicle cannot enter Mexico. I was there one day when some old coot had a motorhome with a temporary plate. He did not want to pay the price for registering in his home state and have to buy US insurance, His answer was "NO Way Jose!". The coot argued away. Bad idea. The ombudsman told him to be polite and to turn around and go home!!! But I digress. Anyone who wants to know the rule about motorhomes can ask at his booth. Posting a cut and paste is of no help. One needs to find the rule for motorhomes not cars and trucks.
Moisheh