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Trane E3.4: Open pressure switch, 2nd stage: PS2 is open when it should be closed

Ref. TRANE-E3-4 · From the Trane furnace manual · Updated 2026-10-23

Status codeE3.4Trane
What it means

Open pressure switch, 2nd stage: PS2 is open when it should be closed.

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How it shows: 7-segment display alternates with mode: E3.4

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§1Likely causes

  • Obstructed pressure switch hose or flue piping, or incorrect vent size
  • Inducer motor not running
  • PS2 not oriented correctly
  • Faulty pressure switch

§2Safe DIY steps

  1. Check outdoor vent and intake terminations for blockage
  2. Techniciancheck PS hose, flue piping and vent size
  3. Techniciancheck inducer and pressure switch
Safety firstIf you smell gas, do not touch any electrical switch or use a phone in the building; leave immediately and call your gas supplier from outside. Turn off electrical power at the furnace switch or breaker before opening any panel, and never bypass or jumper a limit, rollout or pressure switch. Gas valve, burner, venting, wiring and control-board work should be done by a licensed HVAC technician.

§3When to call a pro

Call a licensed HVAC technician: if terminations are clear and the code persists.

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§4Other Trane codes

E01Trane

Loss of the IRQ or other internal failures (internal furnace control error).

E04Trane

Open limit: main thermal limit, flame rollout switch, or reverse airflow switch.

E05Trane

Flame detected when it should not be present.

E06Trane

Voltage reversed polarity or bad grounding.

E08Trane

Low flame current, but still strong enough to allow operation.

E09Trane

Open inducer limit switch or condensate pressure switch.