Quote: Originally Posted by
mohfa 
i'm really confused about the difference between the RPM and PID :
do they have the same parameter . i mean are the RPM params same as those of PID
From SAE J1930, PID means "parameter identification". It's an arbitrary identifier (number) assigned to one piece of diagnostic data.
From SAE J1930, RPM means "revolutions per minute". Under OBD-II the engine speed in revolutions per minute is parameter (hex) 0x0C.