FieldBench
Lennox codes

Lennox

2 flash

Lockout

PS closed

Pressure switch is made with the inducer off.

Walk 2 flash in Diagnose

3 plates — walk the one on the cabinet

First check

1 Prove inducer and the live code

Do not pull power — that clears the Lennox ML180 active code. Write 2 flash. Is the inducer spinning on this call? Silent inducer is not a pressure switch. Welded switch or hose holding chimney draft. Not a 96% trap story.

Expect: 120 VAC at the inducer on a heat call. Wheel turning.

If fail: 120 VAC missing → IFC / door switch / incoming power. Voltage + dead motor → inducer.

If pass: Inducer running + this code → trap, hose, switch, vent (step 2).

The rest of the walkthrough is Diagnose.

On the plates

  • Unplug the switch. Water in the hose or a welded disc.
  • 96% residual draft from a shared vent.
  • Welded switch or hose holding chimney draft. Not a 96% trap story.

Plates that use 2 flash

Same number, other makers

2 flash on Lennox is not the same code on these plates.