1+2
Low flame current — run mode
This code typically points to
- Dirty flame sensor
- Weak grounding path
- Marginal flame carryover
- Gas quality issue
Next checks to confirm
- Check flame-rectification current
- Per Lennox ML180UH heating sequence, proof target is 0.5 µA within 4 seconds after gas valve opens, and 1.5 µA or greater in run sequence
- Clean or replace sensor if weak
- Verify grounding path
- Inspect burner carryover and gas delivery
Escalation
Advisory; does not by itself stop operation per published sequence
Reset behavior
Clears when flame signal returns to acceptable range.
Service Soon
Schedule repair