Furnace pressure switch codes on every brand

More fault codes point at the pressure switch than at any other part of a furnace. Here is what each manufacturer's pressure switch codes mean, and why the same switch produces two opposite faults.

Some of the faults listed here are gas-safety faults. Those ones involve the gas valve, the burner compartment, or the heat exchanger — the parts whose failure can put combustion products, including carbon monoxide, into the air the house breathes, and each carries this warning on its own page. Do not keep resetting a furnace that reports one of them in order to hold the heat on. Have it looked at by a licensed technician, and make sure there is a working carbon monoxide alarm on every level of the home, including the level the furnace is on. The conditions that mean stop now.

What the pressure switch does

The pressure switch is a safety interlock that proves the inducer is actually moving air before the control will open the gas valve. It is a simple diaphragm switch connected by a small hose to the inducer housing or the vent. Suction from a running inducer pulls the diaphragm over and closes the contacts; with no suction the contacts sit open.

Why one part produces several different codes

That is why every manufacturer reports two different pressure switch faults rather than one. Stuck open means the inducer is running but the switch never closed — usually a blocked vent or intake, a cracked or disconnected hose, water in the hose or the collector box, or a failed inducer. Stuck closed means the switch was already closed before the inducer started, which the control reads as a switch that cannot prove anything and therefore cannot be trusted. The first is far more common in cold weather; the second normally means a failed switch or a shorted circuit.

Every pressure switch code on this site

47 codes across 12 control families. The meaning is the manufacturer's, from the document listed at the foot of each code page.

Brand	Code	What it reports
Armstrong	9 flashes	Pressure switch failed to close, or opened during a heat demand
Armstrong	10 flashes	Watchguard — pressure switch opened five times during one heat demand
Armstrong	11 flashes	Pressure switch stuck closed before the inducer started
Carrier	Status code 23	Pressure switch did not open
Carrier	Status code 31	Pressure switch did not close, or reopened
Goodman	2 flashes	Pressure switch is closed when it should be open
Goodman	3 flashes	Pressure switch will not close
Goodman	9 flashes	High stage pressure switch stuck open
Goodman	E1	Low stage pressure switch closed at the start of the heating cycle
Goodman	E2	Low stage pressure switch stuck open
Goodman	E8	High stage pressure switch closed at the start of the heating cycle
Goodman	E9	High stage pressure switch stuck open
Goodman	2 red flashes	Pressure switch stuck closed, or an inducer error
Goodman	3 red flashes	First stage pressure switch stuck open, or an inducer error
Goodman	3 double red flashes	Second stage pressure switch stuck open, or an inducer error
Goodman	6 red flashes	Pressure switch cycle lockout
Heil	2 flashes	Low pressure switch closed when it should be open
Heil	3 flashes	Low pressure switch still open 30 seconds after the inducer started
Heil	6 + 2 flashes	Soft lockout — flame lost during run, cycling pressure switch, or blocked condensate
Heil	8 flashes	High pressure switch closed when it should be open
Heil	9 flashes	High pressure switch open when it should be closed
Lennox	Alert code 223	Low pressure switch open
Lennox	Alert code 224	Low pressure switch stuck closed
Lennox	Alert code 225	High pressure switch will not close
Lennox	Alert code 226	High pressure switch stuck closed
Lennox	Alert code 227	Low pressure switch open in run mode
Lennox	Alert code 271	Low pressure switch open — Watchguard
Lennox	Alert code 272	Low pressure switch open in run mode — Watchguard
Lennox	Alert code 276	Furnace calibration failure, or high pressure switch fault
Lennox	E223	Pressure switch failed open
Lennox	E224	Pressure switch failed closed
Lennox	E227	Pressure switch opened during ignition or run
Lennox	E271	Soft lockout — retries exceeded, pressure switch opened
Lennox	E272	Soft lockout — recycles exceeded, pressure switch opened
Rheem	2 blinks	Pressure switch did not close within 10 seconds
Rheem	3 blinks	Pressure switch closed when it should be open
Rheem	2 blinks	Pressure switch failure — switch remains open
Rheem	4 blinks	Pressure switch failure — switch remains closed
Trane	E3.2	Open pressure switch, first stage
Trane	E3.4	Open pressure switch, second stage
Trane	E3.1	Shorted pressure switch, first stage
Trane	E3.3	Shorted pressure switch, second stage
Trane	E09	Open inducer limit switch or condensate pressure switch
York	2 red flashes	Pressure switch stuck closed, or an inducer error
York	3 red flashes	Pressure switch open, or first stage pressure switch open
York	3 double red flashes	Second stage pressure switch stuck open
York	6 red flashes	Pressure switch cycle lockout

Before you work on it

A pressure switch that will not close is often the furnace correctly refusing to fire because the flue is blocked. Bypassing or jumpering it defeats the interlock that prevents combustion products entering the house.

What the fixes cost

The furnace repair cost guide prices a pressure switch at $150–400 with a note that is really the whole story: check for a blocked flue first. Most of the codes above are the switch truthfully reporting a draft problem, so the honest bill is often a clearing — vent obstruction, condensate trap, slipped hose — inside an ordinary service call, not a part. The two genuinely pricier branches: an inducer that can no longer make draft, $300–900 with brand availability driving the spread, and the stuck-closed codes, which usually do mean a physically failed switch or pinched tubing and land nearer the middle of the $150–400 band. A switch replaced against a stuck-open code without anyone examining the venting is the misfire to watch for in a quote.

Do it yourself or call someone?

One check is safely yours: the outdoor intake and exhaust terminations, for snow, ice, leaves or nests — a common real cause of the will-not-close codes and visible without tools. Weather notes help too; a switch that only fails in wind or hard cold is telling the technician where to look. Everything at the switch itself — hoses, trap, and above all any jumper across its terminals — is off limits, because this is the interlock that keeps combustion products moving out of the house. A furnace that will not prove draft is refusing to run for a reason worth respecting.

Other parts

Sources

Every code meaning above comes from the manufacturer document behind its code page:

This site is a reference, not a substitute for a licensed HVAC technician. Gas appliances can leak carbon monoxide and cause fire. Anything involving gas lines, the heat exchanger, or the flame sensing circuit should be handled by a licensed professional. Pages are written with AI assistance from the sources listed on each page and checked against them before publishing.