"- .1/FLR/FR0906010211 34123406IR2 1,EFCS1X,IR1,IR3,,,,ADIRU2 (1FP2),HARD"
From the description of FLR messages in the BEA report, 4 systems identified an IR2 fault during the 1 min correlation window that opened when the first system detected the fault.
IR2 got priority in the message construct because it detected an internal fault.
Because of the X after EFCS1 in the message, EFCS1 only detected a class 2 fault (crew awareness not required).
IR1 and IR3 also detected the IR2 class 1 fault (they were not faulty themselves).
The exact nature of the fault is unknown.
No other system reported an IR2 fault during the correlation window, since the remaining 3 identifier fields separated by comas are empty. If an IR2 fault was detected afer the end of the correlation window the CMC would not have it reported.
We cannot deduce from the message what system detected the fault first.
Incidentally, since IR1 and IR3 were able to detect an IR2 fault, it appears there is some cross talk between ADIRUs undocumented in the FCOM. A few details related to the QF072 accident also suggest this.