What was found
APU BITE INOPERATIVE, DISPLAYED ON CDU WHILE ATTEMPTING TO ACCOMPLISH ETOPS PDC. ACFT GROUNDED. REMOVED ECU REF AMM 49-61-12. VERIFIED THE PSEU APPLIES A GROUND AT D35599B PIN A6 WHEN PUT IN AIR MODE. ECU REINSTALLED REQUIRES OPS WHEN T/S COMPUTER 42203. POWERED UP ACFT WITH EACH DEU INSTALLED INDIVIDUALLY. NO HELP. REPLACED SPCU. NO HELP. RE-INSTALLED ORIGINAL REF MM 24-31-11. OPS NORMAL IAW SAME. REMOVED ECU VERIFIED LABEL 357 AT D3599BC14/014. RESTORED ECU REQUIRES OPS CHECK. SWAPPED OUT SWITCH MODULE P5-28 NEITHER ITEM HELPED, RESTORED ORIGINAL P5-28. FOUND BLADE CONTACT A6 OF D43211J BENT, SHORTED TO CONNECTOR SHELL. RETERMINATED CONTACT REF SWPM 20-74-11. APU BITE OPS NML T/C 78349002 WAS ACCOMPLISHED.