As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER START UP NOTICED EMERGENCY POWER LIGHT ILLUMINATED. VOLTAGED 28 VOLTS BUT LIGHT REMAINED ON. RETURNED TO GATE. MAINTENANCE REMOVED AND REPLACED EMERGENCY POWER SUPPLY 24-35-10-ND RELAY AT 9PD (P/N M83536-2) IAW AMM 24-35-00. EPS S/N ON OFF 502142, P/N 501-1228-04. ALL CHECKS GOOD.