Can confirm the cause. Disconnected my overhead timer panel - and as expected the same fault as above.There is one side effect of this "retrofit" - one permanent fault in Aux. Heater (18).
0266 - Databus
U1121 00  - Missing Message
Luckily there are no practical consequences of that fault.
It appears that connecting Telestart unit without the overhead timer is the cause
Normally as a standard factory option the overhead timer always comes with Telestart.
Next step is to work out coding modification which will clear this fault
Did some coding experiments, however I didn't remove the "6E" from CANbus installation list.
Run basically through all the version codings + a few "unknowns" by changing the coding and then clearing the fault.
5800 = my current working coding, v1
5808 (byte 1, bit 3)
D800 (byte 0, bit 7)
5880 v1 + (byte 1, bit 7)
58D0 v6No luck with any of the above... - your turn now