Wayne Dohnal wrote:
It really does depend on the specific vehicle. Using my Sprinter chassis as an example, there are "zillions" of codes from every computer in the vehicle that can be accessed via the OBD port, but Mercedes has done an effective job of keeping the chassis-specific codes a secret. There are only a few several thousand $ devices that can read the proprietary codes. You'd probably have better luck on a forum dedicated to the chassis type, rather than an RV forum.
X2
Most aftermarket OBD readers have very limited amount of codes they are able to "read". Most of those codes which CAN be read will be for the ENGINE ONLY.
OBDII ports do have ALL codes available but they do not typically release what all the codes mean.
Reading any other codes including transmission and body codes WILL require a very, very expensive reader from the manufacturer of the vehicle.
Your best bet is to take to your vehicle manufacturers dealer, pay the ransom money to have them hook it up to your vehicle ($100-$200?)..
THE DEALER is the ONLY reliable way of getting the body codes read CORRECTLY.