If the sensors weren't getting readings then yes I would expect that the ABS computer would throw a code, disable itself and illuminate the ABS light on the dash.
There is only 2 things it can be at this point, the brake fluid level, and the stability control computer (under e-brake cover). There is an input shaft speed sensor on the transmission but
AFAIK that is only used for S-mode engine RPM calculations. The A/T's have an output shaft speed sensor but pretty sure the M/T's don't have this.