J2000/Sunbird V6-191 3.1L (1992)
2.
Checks for an open switch in drive range.
3.
Be sure "Scan" indicates drive, even while wiggling shifter to test for an intermittent or mis-adjusted switch in drive range.
DIAGNOSTIC AIDS:
If CKT 434 indicates P/N (grounded), while in drive range, the EGR would be inoperative, resulting in possible detonation.
If CKT 434 always indicates drive (open), a drop in the idle may exist when the gear selector is moved into drive range.