Again, without knowing the exact engine product number, I did a decent range search and 3-2 rail function appears in 2004 in Premier steam starting at 20-3130-1. There may be an engine I am not aware of that has 3-2 rail in a PS2 5V, but I just do not know of it. Even then, PS2 3V is not a guarantee to be 3-2 rail. Example 20-3129-1 is PS2 3V but not yet with 3-2 rail function.
There seems to be a range that happened in roughly 2004 starting with 20-3118-1 through 20-3129-1 that are PS2 3V but not 3-2 rail. 20-3117-1 appears to be the last PS2 5V in 2003? It's also, according to the manual, not 3-2 rail switching.