GM Service Manual Online
For 1990-2009 cars only

Voltage is applied continuously from the B/U LAMP fuse through CKT 840 to the transaxle range switch. Voltage is applied through the closed contacts of the transaxle range switch to the right and to the left backup lamps through CKT 24 when the transaxle is shifted into REVERSE. The backup lamps are grounded through CKT 350 to G401.