Thanks for the feedback. I'm happy to help with IMA stuff if I can.
To summarise the technical problem for the forum..
This was a lithium pack with a permanent P0B3B fault. (Battery Voltage Sensor internal Circuit Error.)
It completely disables the IMA so has to be fixed.
Basically Honda UK were useless and just wanted them to replace the pack. £7k
The owner lives a long way from me but had access to people who could take the pack out and replace bits etc so.........
I got the owner to buy a clone HDS £100? so they could properly identify the fault and do some other diagnostics checks, cell voltages etc.
The HDS indicated the BMS board D was likely faulty or there was a wiring issue.
They pulled the pack and did some basic wiring checks for bad connections/broken wires etc to no avail.
I have spare Lithium pack BMS boards so I sent a new D board and they swapped out the board but the fault remained.
Now I have had issues in the past with the HDS software, it's massively complicated and does have some bugs in it.
In this case it looks like the BMS boards are incorrectly identified (reversed) on the screen so they swapped out board A and the car now works fine.
I charged £150 per board, and they could have got away with just swapping out A, but left D in as well as it is a PITA to take the Lithium pack out and apart each time.
Total cost for my help and spare boards was £300 for two BMS boards ( A & D) and several phone calls/many messages with diagnostic advice.
I'm going to look (test/prod) the faulty BMS board when I get it back from the owner later in the week.
IMHO every serious CR-Z owner should really have a clone HDS for troubleshooting.
They are invaluable!