B737 Captain reported a rejected takeoff after receiving a Master Caution for Cowl Anti-Ice at approximately 90 knots. Crew returned to the gate after consulting with maintenance.

Narrative

Taking off from runway XX in ZZZ the FO applied takeoff thrust and called check thrust. Thrust checked normal at around 85% N1. Shortly afterwards a Master Caution light illuminated with 'Anti Ice' illuminated on the six-pack. I looked up to the overhead panel and observed an amber 'Cowl Anti-Ice' light illuminated on the #2 side. I called for a Reject. The FO had begun to retard the thrust levers and I assumed control of the aircraft after my gaze returned down from the overhead panel and I got my bearings outside. I continued the reject. The FO notified the Tower. We were not yet in the high speed regime. I estimate we were at roughly 80-90 knots. (The Autobrakes felt like they kicked in so it must have been around 90 knots but it didn't feel that fast. My eyes were on the overhead when I called for the reject so I did not catch the exact speed were were at.) The aircraft decelerated at a steady pace and we cleared the runway. The FO made the 'remain seated' announcement over the PA. After clearing we performed the rejected takeoff QRC; calculated brake cooldown times and reviewed the QRH for the 'Cowl Anti-Ice' (which was now extinguished after we reduced engine power). I got on the phone with Dispatch and we patched in Maintenance Control. We performed some troubleshooting and we decided to return to the gate.