yo,
It may have had it if equipped w/Optional (on All trim levels) Trailer Towing Package; but many have been hacked by prev owners or "mechanics" when things went south;
In your 88, Trailer Towing Package consisted of;
wiring harness, HD batty, super eng cooling, aux tranny cooler, HD flasher, handling package
see Option list that shows this info here (I believe I gave you the entire 88 Brochure Links in another thread a few months ago)
Look for a connector under bumper that has these wire colors in bold
TSB 89-14-17 Trailer Wiring Colors
Publication Date: JULY 14, 1989
LIGHT TRUCK: 1990 BRONCO, F-150, F-250, F-350
ISSUE: Trailer tow wire harness color codes have been revised to be compatible with SAE color code standards. When hooking up a vehicle to a trailer that has been wired according to the SAE standard, the wire color/circuits will match.
ACTION: Refer to the following Circuit Color Code Chart for the correct color/circuit usage.
CIRCUIT COLOR CODE CHART
CIRCUIT FUNCTION -
OLD COLOR* - SAE COLOR*
Trailer LH Turn/Stop -
LG/O - Y
Trailer RH Turn/Stop -
O/LB - DG
Trailer Brake Lamp From Controller -
R/LG - R/LG
Trailer Electric Brakes Solenoid -
BL/BR - DB
Trailer Back Up -
BK/PK - R/Y
Trailer Ground -
W - W
Trailer Running/Tail -
W/R - BR/W
Trailer Power (Battery Charge) -
Y - O
Trailer Brake Control Feed -
R - R
Color Key - Color Abbreviations
BL-Blue
BK-Black
BR-Brown
DB-Dark Blue
DG-Dark Green
LB-Light Blue
LG-Light Green
O-Orange
P-Pink
R-Red
W-White
Y-Yellow
1988 Ford Bronco Trailer Wiring Harness
Curt T-Connector Vehicle Wiring Harness with 4 Pole Trailer Connector
http://www.etrailer.com/t1-1988_Ford_Bronco.htm
$19.95
•Installs quickly and easily - simply plugs in to factory connectors
◦Does not require cutting or splicing
•Includes installation instructions
Can be used with 5-pole, 6-pole or 7-pole adapters.
Tech Tip: It is always a good idea to apply a small amount of ELECTRICAL grease to all electrical connections to help prevent corrosion.
the white wire from the Curt T-Connector Vehicle Wiring Harness # 55302 is supposed to be grounded to a clean metal surface on the body of your vehicle