94lt1 with 140k miles. Abs inop lamp will not come on at first start up or the first few miles of driving. It will come on after that and stays on the rest of the day. Checked front and rear brk pad thickness. Checked the two front sensors for any damage or cut wires. There seems to be one at the center diff, not sure if that's the rear sensor but wires and connections are good. Brakes feel normal and fluid level is good. My autoxray scanner cannot scan for codes. Haynes manual offers very little troubleshooting info. What else can I check before I pay a shop? Thanks.

 

Chances are, one of the sensors is just bad. Wiring may look good, but sensor itself can be faulty. One at each front wheel and one at the center of the rear diff. Another possibility is the ABS block is bad. Have you tried testing the ABS by "panic" braking to see if it activates?

 

check your third brake light and make sure both bulbs are working and bulb sockets and connections are good. bulb out in the center light can set the abs light