GM Service Manual Online
For 1990-2009 cars only

When the ignition switch is in the ON/START positions, the back fuse applies battery voltage to the following switches:

    • The backup lamp switch (manual transaxle)
    • The transaxle range switch (automatic transaxle)

When you place the manual selector lever or the gearshift control lever in the R position, the switch closes. Battery voltage is applied to the backup lamps within the rear combination lamps. The rear combination lamps are permanently grounded through the junction block at G400.