American Standard Furnace Code E3.1
Soft lockout
The pressure switch is reading closed when the control expects it to be open, which the control calls a shorted pressure switch.
Manual wording: “Shorted Pressure Switch”
Documented for: A951X condensing and A801X induced draft furnaces with the seven-segment IFC display
Likely causes, most common first
- Shorted pressure switch
- Pressure switch contacts stuck closed
- Wiring fault across the pressure switch
When to call a technician
A stuck pressure switch is a safety-proving device. It must be tested and replaced by a technician, never jumpered.
A American Standard furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- Installer's Guide - Upflow/Horizontal and Dedicated Downflow Gas-Fired, Direct/Non-Direct Vent, Single Stage Condensing Furnaces with High Efficiency Motor (88-A951X001-1D-EN) (American Standard Heating and Air Conditioning, A951X040BU3SAB through A951X120DD5SAB single-stage 95% condensing furnaces (Silver 95 family)) · checked 2026-08-25
- Installer's Guide - Upflow/Downflow/Horizontal Left/Right Gas-Fired, Single Stage Induced Draft Furnaces with High Efficiency Motor (88-A801X003-1C-EN) (American Standard Heating and Air Conditioning, A801X026AM2SC through A801X120DM5SC single-stage 80% induced draft furnaces (Silver 80 family)) · checked 2026-08-25