GM Service Manual Online
For 1990-2009 cars only

Voltage is applied at all times from Fuse 29 through circuit 840 to the Park Neutral Position (PNP) switch. When the transaxle is shifted into the REVERSE position, voltage is applied through the closed contacts of the PNP switch to the right and left backup lamps through circuit 24. The backup lamps are grounded through circuit 350 to G402.