It won't have an ODB2 port. Just a 3-wire that uses their scan tool/PDA. If the MIL light isn't on, there are no system errors. RPM restrictions are on the overall RPMs, in 4wd with the diff-loc on and in reverse. If the pod shows its in 4wd loc or the gear selector switch went bad and shows the R light on while in a forward gear, it will also be restricted. Otherwise look to an engine problem, intake problem like a plugged prefilter bag or maybe some locking brakes.