Trane TVR Pro CO Series Service Manual page 69

Procedure
E8
The ODU's address is not in the valid Slave units addresses should be set from
Yes
range 1 1 to 2
No
Replace the outdoor main PCB
Notes:
1. The master unit address should be set as 0, slave units addresses should be set from 1 to 2, and the addresses should not be repeated within one system.
68