First check the switch itself. Using the chart below. To bypass, simply jump B&C on the main harness end.
NEUTRAL SAFETY SWITCH CONTINUITY SPECIFICATIONS
Position Between Terminals
Park ........................................... "B" & "C"
Reverse ........................................ "A" & "E"
Neutral ........................................ "B" & "C"
Drive ................................................ (1)
3 .............................................. "A" & "G"
1-2 ............................................ "A" & "H"
(1) - No continuity should exist between any terminals.
To repair/rebuilld it, check out:
http://www.jeepin.com/features/nss/index.asp