As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
JUST PRIOR TO BRAKE RELEASE; APU TRIPPED OFFLINE AND GOT A STRONG ACIDIC SMELL IN THE FLT DECK AND THROUGHOUT THE ENTIRE AIRCRAFT. OK TO CONTINUE 49-11-01 SP 1 AND SP 2. P6-4 APU CONT COLLARD P6-5 INLET DOOR COLLARD. APU OPS CHECKS OK. NO HISTORY. RAN APU FOR 30 MINUTES; NO DEFECTS NOTED; NO ABNORMAL SMELLS. REFERENCE M/M 49-11-00.