Trane furnace error codes: blinking lights and S9V2 / S9X display codes

By Jason Dearmin · Last reviewed November 14, 2026

Trane and American Standard furnaces report faults in two different ways depending on the control board. Older Integrated Furnace Controls blink an LED, and the number of flashes between pauses is the code. Current S9V2, S9X1, S9X2 and S9B1 condensing furnaces show a code such as E3.2 or E04 on a small 7-segment display and keep a list of the last six faults. The table keeps the two systems separate, so first look through the sight glass or at the control to see which one you have.

What this table coversCodes from three Trane documents: installer's guide 18-CH49D1-1 for the Integrated Furnace Control (IFC) with an LED that flashes, and the August 2026 Installation, Operation and Maintenance manuals FNR-SVX001C-EN (S9V2) and FNR-SVX002B-EN (S9X1, S9X2, S9B1), whose controls show codes on a 7-segment display. The Applies to column shows which document lists each code. A code missing for a model was not in that document; it does not prove the code can never appear. American Standard furnaces with other boards, and other Trane series (S8, XR, XV), can use different tables; check the wiring-diagram label inside your furnace.

How to read the display

LED-flash boards (18-CH49D1-1): count the flashes in one group before the pause. A slow flash with no call for heat is normal, and a fast flash during a call for heat is also normal. A continuously lit LED means Trane says to replace the IFC, and a continuously dark LED means check power. Because the control is polarity sensitive, the hot leg of the 115 VAC supply must connect to the black field lead; 6 flashes points at reversed polarity, poor grounding or low system voltage.

7-segment boards (S9V2, S9X): the code appears on the display, with an E in front (for example E04, E09 or E3.2). The troubleshooting flow charts in the manuals title the same codes "04 Fault Code", "3.2 Fault Code" and so on. To see the last six faults, press the Menu key until L6F appears, then press Option to step through them. Holding Option for at least 5 seconds inside L6F clears the list; three sets of dashes confirm it. Record the codes before anyone clears them, because a technician will want the history.

Codes in the E2, E3 and E04 to E09 groups describe ignition, pressure switch, limit, flame and condensate problems. E10 and higher on the S9V2 are mostly control-board, blower-motor and personality-module faults that only a technician can address.

Trane / American Standard code table

Code	Meaning	Applies to	What the document says
Slow flash	Normal: no call for heat	IFC 18-CH49D1-1 (LED flashes)
Fast flash	Normal: call for heat	IFC 18-CH49D1-1 (LED flashes)
Continuous on	Replace the IFC	IFC 18-CH49D1-1 (LED flashes)
Continuous off	Check power	IFC 18-CH49D1-1 (LED flashes)
2 flashes	System lockout (retries or recycles exceeded)	IFC 18-CH49D1-1 (LED flashes)
3 flashes	Draft pressure error	IFC 18-CH49D1-1 (LED flashes)	Possible problems: a venting problem, a pressure switch problem or an inducer problem. Full explanation
4 flashes	Open temperature limit circuit	IFC 18-CH49D1-1 (LED flashes)	Full explanation
5 flashes	Flame sensed when no flame should be present	IFC 18-CH49D1-1 (LED flashes)
6 flashes	115 volt AC power reversed, poor grounding, or system voltage too low	IFC 18-CH49D1-1 (LED flashes)
7 flashes	Gas valve circuit error	IFC 18-CH49D1-1 (LED flashes)
8 flashes	Low flame sense signal	IFC 18-CH49D1-1 (LED flashes)	Full explanation
9 flashes	Check the ignitor circuit and the line N to 24 VAC common voltage (2 volts or less)	IFC 18-CH49D1-1 (LED flashes)	Trane notes a possible grounding problem.
E01	Internal failure of the control board	S9V2 · S9X1 · S9X2 · S9B1	Replace the IFC.
E2.1	Retry lockout: 3 unsuccessful tries for ignition within one call for heat	S9V2 · S9X1 · S9X2 · S9B1	Lockout lasts one hour.
E2.2	Recycle lockout: 10 recycles within one call for heat	S9V2 · S9X1 · S9X2 · S9B1	Lockout lasts one hour. The S9V2 chart describes it as flame sensed and then lost.
E2.3	1st stage gas valve not energized when it should be, 10 times in the same call	S9V2 · S9X1 · S9X2 · S9B1	Replace the IFC.
E2.4	Redundant relay (HLO output) not energized when it should be, exceeded 10 times	S9V2	Replace the IFC.
E3.1	1st stage pressure switch (PS1) closed when it should be open	S9V2 · S9X1 · S9X2 · S9B1	Trane: in most cases the pressure switch is not the problem; verify pressure switch wiring and tube routing.
E3.2	1st stage pressure switch (PS1) open when it should be closed	S9V2 · S9X1 · S9X2 · S9B1	Trane says PS1 open errors can occasionally occur in wind gusts. The chart checks the inducer, switch orientation, hose and flue piping for obstruction, and vent size. Full explanation
E3.3	2nd stage pressure switch (PS2) closed when it should be open	S9V2 · S9X2
E3.4	2nd stage pressure switch (PS2) open when it should be closed	S9V2 · S9X2
E04	Open limit switch (the S9V2 wiring diagram legend lists open thermal limit, rollout switch or reverse airflow switch)	S9V2 · S9X1 · S9X2 · S9B1	Limit switches open when an abnormal high temperature is sensed. Trane: never leave these switches jumpered. The chart starts with filters and airflow.
E05	Flame sensed when it should not be	S9V2 · S9X1 · S9X2 · S9B1
E6.1	Reversed polarity: incoming high-voltage wiring is reversed	S9V2 · S9X1 · S9X2 · S9B1
E6.2	Faulty ground: incoming or chassis ground connection not sensed	S9V2 · S9X1 · S9X2 · S9B1
E6.3	Igniter relay fault: relay stuck closed (S9V2 also: igniter circuit open or shorted)	S9V2 · S9X1 · S9X2 · S9B1
E7.1	External gas valve circuit error: 24 volts present when it should not be	S9V2 · S9X1 · S9X2 · S9B1
E7.2	Redundant HLO relay closed when it should not be	S9V2	Replace the IFC.
E08	Low flame sense current	S9V2 · S9X1 · S9X2 · S9B1	The flow charts define it as flame sense current below 0.5 micro-amp DC.
E09	Condensate pressure switch open or inducer limit open	S9V2 · S9X1 · S9X2 · S9B1	Condensate not draining freely, or an inducer limit trip, which Trane says is normally caused by improper installation or application of the venting system.
E10	Communication error between the inducer and blower motor microprocessors	S9V2	Replace the IFC.
E11	Internal gas valve relays failed (S9V2 also: 24 VAC sensed at the 2nd stage gas valve)	S9V2 · S9X1 · S9X2 · S9B1
E12	Onboard 5 amp fuse open or missing	S9V2 · S9X1 · S9X2 · S9B1
E13	Blower motor HP or OEM ID does not match the personality module	S9V2
E14	Personality module missing and onboard information cannot be read	S9V2	The S9X manual says E14 and E18 have been reported on S9X2 furnaces at initial start-up and are not valid errors there.
E15	Personality module and IFC information corrupted	S9V2
E17	IFC does not see a return signal from the blower motor	S9V2
E18	IFC does not see its own send message	S9V2	See the E14 note for S9X2.

Sources: Trane 18-CH49D1-1 'SiNi - IFC Error Codes' table (04/09) for the flash rows; FNR-SVX001C-EN (S9V2) and FNR-SVX002B-EN (S9X1/S9X2/S9B1) Troubleshooting fault-code flow charts and definitions for the E rows.

Which document matches my furnace?

Column label	Document	Furnaces covered
IFC 18-CH49D1-1	Installer's guide 18-CH49D1-1 (04/09), SiNi igniter assembly IGN00117	Trane and American Standard furnaces with the LED-flash Integrated Furnace Control described in the guide
S9V2	IOM FNR-SVX001C-EN (August 2026)	S9V2B040 through S9V2D120, upflow/horizontal and dedicated downflow, 2-stage variable speed with variable speed inducer
S9X1 · S9X2 · S9B1	IOM FNR-SVX002B-EN (August 2026)	S9X1 and S9B1 single-stage, S9X2 two-stage condensing furnaces with high efficiency motor

Winter quick guide For pressure switch codes (3 flashes, E3.1 to E3.4) start with our E3.2 page and the cross-brand pressure switch guide. For limit codes (4 flashes, E04) start with the filter and supply and return vents. E09 can mean the condensate is not draining freely; the S9X manual separately cautions installers to take measures to prevent drains from freezing, so a drain line through a cold garage or crawlspace is worth mentioning to your technician.

Detailed explanations

SafetyThese tables describe what the manufacturer documents say. Gas, combustion, refrigerant and line-voltage repairs are for licensed professionals. If you smell gas, leave the building and call your gas utility or 911. Safety disclaimer.

Sources

Installer's Guide 18-CH49D1-1: SiNi Igniter Assembly IGN00117 (includes the Integrated Furnace Control error flash codes) (Trane) Covers: Trane and American Standard furnaces using the Integrated Furnace Control (IFC) covered by this installer guide (dated 04/09). Newer boards can differ; check the wiring-diagram label inside your furnace.
Installation, Operation, and Maintenance FNR-SVX001C-EN (August 2026): S9V2 2-Stage Condensing Variable Speed Furnaces with Variable Speed Draft Inducer (Troubleshooting, Fault Code flow charts) (Trane) Covers: Trane S9V2 upflow/horizontal and dedicated downflow condensing furnaces (S9V2B040 through S9V2D120) with the 7-segment display IFC.
Installation, Operation, and Maintenance FNR-SVX002B-EN (August 2026): S9X1, S9X2 and S9B1 Single Stage / Two Stage Condensing Furnaces with High Efficiency Motor (Troubleshooting) (Trane) Covers: Trane S9X1 and S9B1 single-stage and S9X2 two-stage condensing furnaces with the 7-segment display IFC.