Do I need the sensor rotor if abs is disconnected

the abs gets it signals from the sensors at every wheel
these sensors read from the hubs or disc rotors so make sure that the rotors or hubs have the required exciter inbuilt for the sensors to read
check for damaged wires to the wheels as any one damaged /disconnected will put the ABS on

Each wheel has a magnetic sensor and a slotted ring that generates the ABS pulse. The sensor can get dirty (rust, mud and brake dust) and have to be cleaned. The replaceable slotted ring often rusts in older cars. The cable from the wheel sensors to the body, while very tough, can get damaged or disconnected. Its usually the front ones.

You may need new rotors.
Subarus requires the same make and size of tires front and rear. Mixing sizes can cause a mismatch in the ABS signals from each end, and this will often cause the ABS light to come on.
The ABS computer may have failed.

If ABS is working more or less correctly, hitting the brakes on loose dirt or snow/ice should result in the pedal kick back and the buzzing of the ABS valve system.

Interesting question. The ABS magnetic sensors on each wheel can get gummed up with dirt, rust and brake dust. Perhaps the brake shop did not clean the sensor properly, or worse, may have damaged one or more when the rotors are replaced. The sensor also has a tough wire up to the chassis. If this is damaged or disconnected, the ABS light will turn on.

Take it back to the shop and have them check.

I would be rechecking the rotor position and sensor position on the hub you were working on . check for disconnected wiring or rotor to sensor clearance for the ABS system.

A front brake pulsing with no ABS light is a rotor that is no longer true i.e warped. Pull off the tire and rotate the rotor. Hold a straight edge (ruler) across the outside of the rotor as your rotating the rotor. You will note that it changes distance on the straight edge / ruler as it rotates. (in out wobble) A good way to test for an out of true rotor is to drive at about 45 miles and hour and really stand on the brakes (do not lock them up) If the steering wheel and or brake pedal pulsate... you most likely have a rotor problem. If your rotor has never been "turned" it is probably time to do so.

The ABS sensor is behind the rotor on the lower control arm pointed outward toward the rotor with a flat button face. You can not see the button face with the rotor installed. If the sensor is bad you will have an ABS light. I think your troubleshooting the wrong problem. i.e rotor vs your current focus of the ABS sensor.

I would like some feed back on the running dynamic on the road brake test.

Thanks for choosing FixYa,
Kelly

is abs light on??? if so have it checked for codes

if not probably warped rotors replace rotors and pads

On OBD2 vehicles,1996 & up, You need to disconnect battery for an hour or two to discharge memory in computer. Let it sit disconnected for 2 hours. If you cured the problem it will be out & stay out. If it is on there still is an abs problem. Make sure all abs sensors are connected properly & no broken or crimped wires in their harness.

try unbolting the front abs sensors and cleaning rust off from where they bolt to.these vehicles build up rust under the sensor and create a bigger gap

you do not need to disable thesystem the sensor is incorporated in the wheel bearing

I got the same problem and checking out to solve it found out that a cable from the sensor was cut, repair the cable and restart the failure code disconnecting the battery for at keast 10 min