The following is directly applicable to the 89:
Backup lamps are supplied by I/P fuse # 5. Swtching is performed by the backup lamp switch which is mounted on the top of the transaxle. The Purple/Orange wire is the supply line from the fuse and is hot only when the ignition switch is in RUN. When the transmission is switched into REVERSE, the switch is closed and power is routed to he backup lamps via a Black/Pink wire.
On an ATX, the backup lamp is replaced by a different switch (same location)that is called (depending on the year) the Backup/Neutral Start Switch or the Transmission Range Selector or the Manual Lever Position Switch/Sensor.
Check the individual schematic for your exact vehicle to determine which fuse supplies the backup lamps. Some used #1, Some use #5.
Steve
<small>[ June 14, 2003, 08:32 AM: Message edited by: projectSHO89 ]</small>