As you probably know, the manual is very good ... but does not include a schematic (circuit diagram).

However ... before you start digging into chip-level fault finding, have you had a good look for "loose connections"? think

By the way, (for me) the interesting thing about this equipment is that it uses the CAN* Bus (which was developed by Bosch for use in motor vehicles)! smile

* Controller Area Network

If you don't inspect ... don't expect.