As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
GATE RETURN, STRONG ACRID ODOR PERMEATED THE CABIN ON TAXI OUT. R & R K5 RELAY AND SPDA 2 DC POWER MODULE IAW AMM 24-61-13. OPS CHECK GOOD. THERE WERE 2 FANS THAT WERE REPLACED IN THE PROCESS, 1 DURING TROUBLESHOOTING AND ANOTHER GOT OVERHEATED AND THAT IS HOW IT WAS DISCOVERED THAT THE POWER BEING SUPPLIED TO THE FAN WAS THE ISSUE. THE FAILED DC POWER MODULE WAS CAUSING THE ODOR.