Took off one morning and ABS light and brake stay on and truck want idel. But brakes work fine and truck runs good. Could this be a vacum line problem? If so where should I look.

Chances are the speed pickup on the differential is either faulty or drity. I had the same thing happen to my 1998 Dodge Ram 2500. In addition to your symptoms, my speedometer stopped working below 25 mph.
this

the part number at Autzone = SU3356 . That is for ABS on rear wheels only. It is a different part number if you have 4 wheel ABS.
this is how to test if it is bad:


TESTING (1997 Models)

Resistance

1. Raise and safely support the vehicle securely on jackstands.
2. Ensure the ignition key is in the OFF position.
3. Disconnect the speed sensor electrical harness.
4. Measure resistance between the terminals on the speed sensor
5. Resistance should be 1000-2500 ohms.
6. If resistance is not within specification, check the harness for continuity.
7. If continuity exists, the sensor is faulty.

1. Raise and safely support the vehicle securely on jackstands.
2. Remove the sensor from the differential.
3. Measure and record the distance from the underside of the sensor flange to the end of the sensor pole piece. This distance represents dimension "B". This dimension should be 1.07-1.08 in. (27.18-27.43mm). If dimension is not within specification, replace the speed sensor.
4. Measure and record the distance between the sensor mounting surface of the differential case and the teeth at the top of the exciter ring. This distance represents dimension "A". This dimension should be 1.085-1.120 in. (27.56-28.45mm). If dimension is not within specification, replace the exciter ring.
5. Subtract dimension "B" from dimension "A" to determine sensor air gap. The gap should be 0.005-0.050 in. (0.127-1.27mm). Took off one morning and ABS light and brake stay - icn_arrow.gif /> Back to Top
   
   Here is how to replace it:
   
   REMOVAL & INSTALLATION
   
   
   
   1. Raise the vehicle.
   2. Remove the brake line mounting nut, if fitted, and remove the brake line from the sensor stud.
   3. Remove the mounting stud from the sensor and shield.
   4. Remove the sensor and shield from the differential housing.
   5. Disconnect the wire and remove the sensor.
   
   To install:
   
   1. Connect the harness to the sensor. Be sure the seal is securely in place between the sensor and wiring connector.
   2. Install O-ring on sensor if removed.
   3. Install sensor on differential; housing, sensor shield, mounting stud. Tighten to 18 ft. lbs. (24 Nm).
   4. Install the brake line on the sensor stud and install the nut.
   5. Lower the vehicle.