SWITCH-BACK UP LAMP
DESCRIPTION
Vehicles equipped with a manual transmission have a
normally open, spring-loaded plunger type backup
lamp switch (2). Vehicles with an optional electronic
automatic transmission have a Transmission Range
Sensor (TRS) that is used to perform several func-
tions, including that of the backup lamp switch. The
TRS is described in further detail elsewhere in this
service information.
The backup lamp switch is located in a threaded hole
on the side of the manual transmission housing. The
switch has a threaded body and a hex formation near
the plunger end of the switch. An integral connector
receptacle at the end of the switch opposite the
plunger connects the switch to the vehicle electrical
system through a take out and connector of the
engine wire harness. When installed, only the switch
connector and the hex formation are visible on the
outside of the transmission housing. The backup lamp
switch cannot be adjusted or repaired and, if faulty or
damaged, the entire switch unit must be replaced.
OPERATION
The backup lamp switch controls the flow of battery voltage to the backup lamp bulbs through an output on the
backup lamp feed circuit. The switch plunger is mechanically actuated by the gearshift mechanism within the trans-
mission, which will depress the switch plunger and close the switch contacts whenever the reverse gear has been
selected. The switch receives battery voltage through a fuse in the Integrated Power Module (IPM) on a fused igni-
tion switch output (run) circuit whenever the ignition switch is in the On position. The backup lamp switch and cir-
cuits can be tested using conventional diagnostic tools and methods.
DIAGNOSIS AND TESTING
BACKUP LAMP SWITCH
1. Disconnect and isolate the battery negative cable.
2. Raise and support the vehicle.
3. Locate and disconnect the engine wire harness connector for the backup lamp switch.
4. Check for continuity between the two terminal pins in the backup lamp switch connector receptacle.
a. With the gear selector lever in the Reverse position, there should be continuity.
b. With the gear selector lever in any position other than Reverse, there should be no continuity.
5. If the switch fails either of these two continuity tests, replace the faulty backup lamp switch.
8L - 90
LAMPS/LIGHTING - EXTERIOR - SERVICE INFORMATION
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