Bryant Furnace Code 31.6
WarningShown as: Major code 31 on the LED (3 short, 1 long); 31.6 on the display
Open secondary pressure switch - the high-heat pressure switch did not close for one minute after the gas valve closed, or it has reopened.
Manual wording: “31.6 OPEN SECONDARY PRESSURE SWITCH - HPS did not close for one minute after gas valve closed or has reopened.”
Documented for: 926TC
Likely causes, most common first
- Failed to close secondary pressure switch after three trials
- Excessive wind
- Restricted vent
- Defective inducer motor
- Low inlet gas pressure (if LGPS used)
- Inadequate combustion air supply
- Improper vent sizing
- Disconnected or obstructed pressure tubing
- Condensate drainage restricted or blocked
What you can safely check yourself
- Check the outdoor intake and exhaust pipes for blockage from snow, ice, leaves, or nests
- Check the condensate drain line and trap for a clog
When to call a technician
Vent sizing, inducer performance, and pressure switch calibration are technician diagnostics.
A Bryant furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Source
- Installation, Start-up, Operating and Service and Maintenance Instructions - 926TC (Bryant Heating & Cooling Systems, 926TC Preferred Series two-stage, variable-speed ECM multipoise condensing gas furnace) · checked 2026-08-25