Error Code 5A

[daneli]

DataScan reports the following through the Self Diagnostics function:
"Code 5A > Car started 245 times with this fault"
This code isn't listed in the Appendix to the DataScan user manual and so far I can't find it listed anywhere online either. Does anyone know what code 5A is?

Thanks!

PS: Car is a 1999 Infiniti G20 (=P11)

[Tom]

5A = P0138 Rear heated oxygen sensor (max. voltage monitoring)