Lennox Error Code Off / Off

Full Diagnosis

No Power / Board Dead. Both status LEDs on the DS1/DS2 control board are completely dark, meaning the board isn't seeing line voltage or 24V control power at all — this is different from an E-code lockout, where the LEDs actively flash a pattern. With no power at the board, the inducer never prepurges, the igniter never warms, and the blower stays off. Confirm 120V is present at the furnace disconnect/junction box and that the blower door is fully seated, since the door interlock switch cuts power to the board whenever the door is open or misaligned.

All Recorded Causes

Tripped breaker or open service disconnect, blown line-voltage fuse on the control board, blower access door not fully closed (open door/interlock switch), loose or backed-out wire nut at the 120V junction box, failed step-down transformer, or a bad thermostat harness connection preventing the board from powering up.

Verify Before Replacing Parts

1. Confirm the exact Lennox model family and ds1 & ds2 context before acting on a generic code description.
2. Walk the entire heating sequence in order instead of jumping straight to the reported code, watching for tripped breaker or open service disconnect, blown line-voltage fuse on the control board,….
3. Verify each safety device and prove where the sequence stops under live operation, including whether the next candidate on the list.
4. After the correction, run the system long enough to confirm the ds1 & ds2 fault does not return under normal load.