GM-GMC: abs brake light, wheel sensors, obd system

Question
Hello Harry, I own a 1990 gmc k-1500 sierra 4x4 x/c pickup...The brake system/abs light,only one light for two functions, either stays on all the time or it blinks 10-times continuesly..I have put on new brakes f&b, rotors and drums and also replaced the wheel cylinders and I even tried another abs module and the light still came back on... I also checked the emegency brake switch and that appears fine.. I have had this problem since I bought this truck a year ago..I do-not see any front wheel sensors or wires or a abs speed sensor on the transmisson of this truck....WHAT DO YOU THINK???? THANX TONY..

Answer
The sources I have state that the vehicle has an ABS system.  There is a control module and a differential sensor.  It may be that it only works on the rear brakes (by sensing differential speed) and there would be no wheel sensors in that case.  Check the differential for a sensor.

I don't have a vehicle with ABS.  I do not know if your vehicle's OBD system records faults for the brake system.  Most auto parts stores will read codes for free.  You might try to have the codes read or replace the differential sensor.