Ron, is correct in the code.  They are found on a flat place in the block right below the Crankcase Ventilation Tower (black tower looking thing on the motor, to the right of the center line).  Just take some brake cleaner with you because normally the code if covered by dirt and oil.  Or you can just look in the door jamb as you can almost bet that an 83-85 Vanagon will have a DH (1.9l) engine and a 86-91 will have a MV (2.1l)(unless there has been a conversion project, which is rare to find in the junk yard).

Thanks,
Ken Wilford
John 3:16
www.vanagain.com
Phone: (856)-765-1583
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