b1 checks
| Step | Check | If yes | If no / next |
|---|---|---|---|
| 1 | In the second service level, service function 8.b (code plug). Compare digits 7–10 of the order number. Missing or incorrect number? | Go to step 2. | Go to step 3. |
| 2 | Code plug loose, incorrect, or defective? | Power off, fit the correct code plug, power on. If b1 remains, go to step 3. | |
| 3 | PCB damaged | Note service settings, replace the PCB, restore settings. |
Gas work stays with a Gas Safe registered engineer. These steps are guidance from the manufacturer sequence, not a substitute for the handbook.