there are numerous different tools to connect to different vendors emission control system, and in the forklift world, there are no real "aftermarket" scanners.
the manufacturers' dealer representatives have a mandate from the C.A.R.B to insure that only properly trained personal are allowed to access software that can adjust the emission system, and using [what I consider to be] an over abundance of caution they have interpreted that to mean 'if that dealer has not taught you, [and registered your information with the factory] then they do not have to sell you any method to connect to the truck.
All that said, in about 95% of all forklifts sold in the USA since 2004, about 98% of all diagnosis and repair can be done without any 'scan tool' or computer at all.