Check the sync setting on your electric brake controller along with the sensitivity setting. If you've readjusted your trailer brakes you also have to reset your settings on the brake controller. Pulsating is generally caused by the sync setting being to high and or the sensitivity setting to high. A simple fix just drive down a side street or parking lot and adjust the sync to +/- till it stops pulsating then again adjust the sensitivity as to how soon the brakes apply and how hard.