1992 to 1995 have the OBD1 computer, 1996 on up are the OBDII computers. Each one is programmed for each motor size.
There is a calibration code for each vehicle that is manufactured and there is a computer that matches that code, that is why the numbers must match when the computers are replaced, the only exception is when the factory does an upgrade to correct a problem then a tag is placed on the vehicle stating that was done, so if there is a problem down the road then you have the upgraded numbers.
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