no such luck (that forklifts would use some older form of self diagnostics common to most in the same year range) heck there are same model size and year ranges that don't use the same diagnostics. and any thing built before about 2002 will be "old-school" diagnostics anyway.
I see where you put "2.2L propane diagnostics". but I did not know which of the 2 different designations was the correct one. ;-)
We (in the forklift repair business) more often use the motor designation (4y), but since these machines sometimes get "rigged" with non-oem parts and sort of redesigned it is often better to give as correct much information as possible, so to not have it confused with other possible configurations. We also use the model and serial numbers since these machines may be manufactured and sold in differing years, and which year of manufacture/design would be designated by the model and serial number.
all that said, in 2004, I am pretty sure there were 2 different options for emission/carburation controls on LPG powered 4y motors that Toyota used, one was called ECS (a drive by wire-electronic throttle body) and TWC (three way catalytic converter with a throttle cable connection to the carburator). these use differing systems and different places to jumper to read out "flashing light codes". let us know which one you have and then we can go from there.