Trane Furnace Code E3.1
Soft lockout
The first-stage 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, 1st Stage”
Documented for: S8V2, S9V2 and S9V2-VS furnaces; on single-stage S8B1 the same code reads simply 'Shorted Pressure Switch'
Likely causes, most common first
- Shorted pressure switch, 1st stage
- 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 Trane 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 Downflow Gas-Fired, Direct/Non-Direct Vent, 2-Stage Condensing Variable Speed Furnaces (18-CE01D1-1E-EN) (Trane, S9V2B040U3PSAA through S9V2D120D5PSAA two-stage condensing variable-speed furnaces) · checked 2026-08-25
- Installation, Operation, and Maintenance - Gas-Fired 2-Stage Condensing Variable Speed Furnaces with Variable Speed Draft Inducer (FNR-SVX001B-EN) (Trane, S9V2B040U3VSBB through S9V2D120D5VSBB (S9V2-VS) two-stage condensing variable-speed furnaces) · checked 2026-08-25
- Installation, Operation, and Maintenance - Link Communicating or 24 Volt Gas-Fired 2 Stage Induced Draft Furnaces with Variable Speed Motor (FNR-SVX003A-EN) (Trane, S8V2A040M3PCB through S8V2D120M5PCB two-stage 80% induced draft furnaces (communicating or 24V)) · checked 2026-08-25