There is a single wire plug on the side of the hood release bracket under the dash. It's the RWAL test connector in a 91

If the anti-lock light is always on, it will show the fault code if momentarily grounded.
Long first flash is not counted. Count short flashes after long flash for fault code


1- Not used
2-Open isolation valve wiring or bad control module
3-Open dump valve wiring or bad control module
4-Closed RWAL valve switch
5-Over 16 dump pulses generated in 2wd vehicles(disabled for 4wd)
6-Erratic speed sensor reading while rolling
7-Electronic control module fuse pellet open, isolation output missing, or valve wiring shorted to ground
8-Dump output missing or valve wiring shorted to ground
9-Speed sensor wiring/resistance(usually high reading)
10-Sensor wiring/resistance ( usually low reading)
11-Brake switch always on. RWAL light comes on when speed exceeds 40 mph
12-Not used
13-Electronic control module phase loop failure
14-Electronic control module program check failure
15-Electronic control module RAM failure


I would unplug the module behind the glove box ( straight inside) before worrying about trouble shooting. Mine acted up one time and that was the fix...needed to be reset. Disconnect for 5 seconds.