Trane and American Standard Furnace Codes by Series
A current Trane or American Standard furnace shows a fault as an E-code, such as E2.1 or E04, on the small display of its control board; older furnaces flash a red LED a set number of times. The same code can read differently between series, so find your series first. Every meaning below is copied from the manufacturer's own installation manual, with document number and page.
Key facts
| Fact | Detail |
|---|---|
| Series covered | Trane S9X1, S9X2, S9B1, S8X1, S8X2, S8V2 and S9V2-VS; American Standard A801X, A951X and A952V; older Trane and American Standard furnaces fitted with replacement-control kits 18109, 17399 and 20350 |
| Where the meanings come from | Installation, operation and maintenance manuals FNR-SVX002B-EN, FNR-SVX008A-EN, FNR-SVX003A-EN, FNR-SVX001C-EN, A801X-SVX001-1D-EN, FNR-SVX004B-EN and FNR-SVX005B-EN, and service installer's guides 18-CH92D1-1A-EN, 18-CH76D1-1A-EN and 18-CH111D1-1A-EN, all in Trane Technologies' public eLibrary |
| How current furnaces show a fault | An E-code on the "7 Segment LED" display of the integrated furnace control (IFC) |
| How older furnaces show a fault | A count of red LED flashes; a slow or fast green flash is normal operation |
| Readings that are not faults | IdL (idle), Ht, Ht1, Ht2 (heating), CL1, CL2 (cooling), HP1, HP2 (heat pump), COF (continuous fan), dFt (defrost) |
| Lockout | E2.1 and E2.2 end in a one-hour lockout; we found no homeowner reset procedure in these manuals |
| Last checked | October 29, 2026 |
How to find your series
The model number on your furnace starts with the series: Trane's manuals list their models in full on the cover, from S9X1 and S9X2 to S9V2B040U3VSBB, and American Standard's from A801X040AM3SDA/B to A952V120DU5SB. Match the start of your model number to a row below. If it matches none of them, this page does not cover your furnace.
| Series as printed | Brand | Manual (revision used here) | How it shows a fault | Section |
|---|---|---|---|---|
| S9X1, S9X2, S9B1 | Trane | FNR-SVX002B-EN | E-code on display | jump |
| S8X1, S8X2 | Trane | FNR-SVX008A-EN | E-code on display | jump |
| S8V2 | Trane | FNR-SVX003A-EN | E-code on display | jump |
| S9V2-VS | Trane | FNR-SVX001C-EN | E-code on display | jump |
| A801X | American Standard | A801X-SVX001-1D-EN | E-code on display | jump |
| A951X | American Standard | FNR-SVX004B-EN | E-code on display | jump |
| A952V | American Standard | FNR-SVX005B-EN | E-code on display | jump |
| *DD, *DC (1990–1999), *UD2, *DD2, TUX, TDX, AUX, ADX with a replacement control | Trane or American Standard ("* May be "A" or "T"") | 18-CH92D1-1A-EN, 18-CH76D1-1A-EN, 18-CH111D1-1A-EN | Green and red LED flashes | jump |
The older kit guides are why this page covers both brands: each prints one diagnostic table for models whose leading letter "May be "A" or "T"", or, in 18-CH111D1-1A-EN, for a model list that mixes TUX and TDX with AUX and ADX. The current American Standard series have their own manuals, and their tables are given separately below rather than borrowed from the nearest Trane series.
How to read a Trane or American Standard code
On the current furnaces the code is on the integrated furnace control's seven-segment display, and it alternates with what the furnace is doing. Trane's wording (FNR-SVX002B-EN, p. 95): "If an error occurs, an E*.* will alternately flash with the system mode and airflow request." The same page explains that "The status will alternate between the system mode and the airflow request every 2 seconds,", and the error alternates with them.
The status codes that are not faults are listed on the same page: "IDL = Idle, no demand for cooling, heating, or fan", "HT1 = Demand for 1st stage gas heat", "HT2 = Demand for 2 nd gas heat", "COF = Demand for continuous fan" and "DFT = Demand for outdoor unit defrost, furnace running in gas heat mode". The S9V2-VS manual adds Lr1 and Lr2, "First Stage Gas Heat Learning Routine" and "Second Stage Gas Heat Learning Routine", and ArF, "Calculated Airflow (Followed by Airflow times 10)" (FNR-SVX001C-EN, Table 38, p. 82).
The control also keeps a fault history. Every current manual here describes a "Last 6 Faults" (L6F) menu reached with the board's Menu and Option keys, and says the history is cleared by holding "Option" for at least 5 seconds (FNR-SVX002B-EN, p. 99). The manuals open with the line "Only qualified personnel should install and service the equipment." (FNR-SVX002B-EN, p. 1)
Lockouts
E2.1 and E2.2 are lockouts. The S9X manual's troubleshooting chart defines the first one (FNR-SVX002B-EN, p. 102): "RETRY Lock Out = 3 unsuccessful tries for ignition within a single call for heat. Lockout period is for one hour." E2.2 is "Recycles Exceeded (Flame sensed then lost, one hour lockout after 10 times)" in every table that has it.
The number of ignition tries before the lockout is not the same everywhere: 3 on the S9X1, S9X2, S9B1, S8X1, S8X2, A801X and A952V, 6 on the A951X, and 7 on the S8V2. We found no homeowner reset procedure in these manuals. A code that keeps coming back after the lockout ends is a job for a qualified servicer.
S9X1, S9X2 and S9B1 codes
The S9 condensing furnaces in single stage (S9X1, S9B1) and two stage (S9X2) share one manual and one table, Table 43 of FNR-SVX002B-EN. The second-stage codes are marked as not applying to the single-stage S9X1 and S9B1.
| Code | Trane's alarm explanation (verbatim) | Page |
|---|---|---|
| E01 | Loss of the IRQ or other internal failures (Internal IFC error) | 98 |
| E2.1 | Retry Exceeded (Flame never sensed, one hour lockout after 3 times) | 98 |
| E2.2 | Recycles Exceeded (Flame sensed then lost, one hour lockout after 10 times) | 98 |
| E2.3 | 1st Stage Gas Valve Not Energized When It Should Be exceeded after 10 times | 98 |
| E3.1 | Shorted Pressure Switch, 1st Stage | 98 |
| E3.2 | Open Pressure Switch, 1st Stage | 98 |
| E3.3 | Shorted Pressure Switch, 2nd Stage (Not applicable for S9X1/S9B1) | 98 |
| E3.4 | Open Pressure Switch, 2nd Stage (Not applicable for S9X1/S9B1) | 98 |
| E04 | Open Limit (Main Thermal, Rollout Switch, or Reverse Airflow Switch) | 98 |
| E05 | Flame detected, should not be present | 98 |
| E6.1 | Voltage reversed polarity | 98 |
| E6.2 | Bad grounding | 98 |
| E6.3 | (1) Igniter relay fails (2) Igniter open | 98 |
| E7.1 | 1st Gas valve (MVL) is energized when it should be off | 98 |
| E08 | Flame current is low, but still strong enough to allow operation | 98 |
| E09 | Open Inducer Limit Switch or Condensate Pressure Switch | 98 |
| E11 | (1) 1st stage gas valve not energized when it should be (2) 1st stage gas valve relay stuck closed (3) 2nd stage gas valve relay stuck closed (Not applicable for S9X1/S9B1) (4) 2nd stage gas valve energized when it should not be (Not applicable for S9X1/S9B1) (5) 2nd stage gas valve not energized when it should be (Not applicable for S9X1/S9B1) | 98 |
| E12 | Open fuse | 99 |
| E14 / E18 | Refer troubleshooting flow chart | 99 |
S8X1 and S8X2 codes
The S8X1 (single stage) and S8X2 (two stage) induced-draft furnaces use the same list as the S9 furnaces, without E09 or E14/E18, in Table 34 of FNR-SVX008A-EN. This October 2026 manual supersedes S8XB-SVX001-1D-EN.
| Code | Trane's alarm explanation (verbatim) | Page |
|---|---|---|
| E01 | Loss of the IRQ or other internal failures (Internal IFC error) | 60 |
| E2.1 | Retry Exceeded (Flame never sensed, one hour lockout after 3 times) | 60 |
| E2.2 | Recycles Exceeded (Flame sensed then lost, one hour lockout after 10 times) | 60 |
| E2.3 | 1st Stage Gas Valve Not Energized When It Should Be exceeded after 10 times | 60 |
| E3.1 | Shorted Pressure Switch, 1st Stage | 60 |
| E3.2 | Open Pressure Switch, 1st Stage | 60 |
| E3.3 | Shorted Pressure Switch, 2nd Stage (Not Applicable for S8X1) | 60 |
| E3.4 | Open Pressure Switch, 2nd Stage (Not Applicable for S8X1) | 60 |
| E04 | Open Limit (Main Thermal, Rollout Switch, or Reverse Airflow Switch) | 60 |
| E05 | Flame detected, should not be present | 60 |
| E6.1 | Voltage reversed polarity | 60 |
| E6.2 | Bad grounding | 60 |
| E6.3 | (1) Igniter relay fails (2) Igniter open | 61 |
| E7.1 | 1st stage gas valve (MVL) is energized when it should be off | 61 |
| E08 | Flame current is low, but still strong enough to allow operation | 61 |
| E11 | (1) 1st stage gas valve not energized when it should be (2) 1st stage gas valve relay stuck closed (3) 2nd stage gas valve relay stuck closed (Not Applicable for S8X1) (4) 2nd stage gas valve energized when it should not be (Not Applicable for S8X1) (5) 2nd stage gas valve not energized when it should be (Not Applicable for S8X1) | 61 |
| E12 | Open fuse | 61 |
S8V2 codes
The S8V2 is a two-stage induced-draft furnace with a variable-speed motor, built for a "Link Communicating or 24 Volt" system, and its control has the longest list: the open limit splits into three codes (E4.0, E4.1, E4.2), and E13 to E28 cover the blower, the configuration file and the air sensors. Table 37 of FNR-SVX003A-EN, which supersedes S8V2-SVX001B-EN.
| Code | Trane's alarm explanation (verbatim) | Page |
|---|---|---|
| E01 | Loss of the IRQ or other internal IFC failures | 59 |
| E2.1 | Retries exceeded (Flame never sensed, one hour lockout after 7 times) | 59 |
| E2.2 | Recycles exceeded (Flame sensed then lost, one hour lockout after 10 times) | 59 |
| E2.3 | 1st stage gas valve not energized when it should be (10 times) | 59 |
| E3.1 | Shorted pressure switch, 1st stage | 59 |
| E3.2 | Open pressure switch, 1st stage | 59 |
| E3.3 | Shorted pressure switch, 2nd stage | 59 |
| E3.4 | Open pressure switch, 2nd stage | 59 |
| E4.0 | Open high limit switch | 59 |
| E4.1 | Open reverse air-flow limit switch | 59 |
| E4.2 | Open roll-out limit switch | 59 |
| E05 | Flame detected when it should not be present | 59 |
| E6.1 | Voltage reversed polarity | 59 |
| E6.2 | Bad grounding | 59 |
| E6.3 | (1) Igniter open or igniter relay failure on IFC (2) Igniter relay failure on IFC | 59 |
| E7.1 | 1st stage gas valve energized without request | 59 |
| E7.2 | Redundant relay (HLO output) energized when it should not be | 59 |
| E08 | Low flame sense. Current is low but strong enough for operation | 59 |
| E11 | (1) 1st stage gas valve not energized when it should be (2) 2nd stage gas valve energized without request (3) 2nd stage gas valve not energized when it should be (4) Gas valve relay stuck closed | 59 |
| E12 | Open fuse | 59 |
| E13 | Blower HP or OEM ID do not match furnace | 59 |
| E14 | Configuration file error | 60 |
| E17 | Blower communication error | 60 |
| E23 | Menu parameters not received by CCM | 60 |
| E24 | Internal communication error between the ACM and CCM | 60 |
| E25 | Orientation sensor out of bounds | 60 |
| E26 | 1) Return static pressure transducer out of bounds 2) Return static pressure transducer configured but not connected | 60 |
| E27 | 1) Return air thermistor out of bounds 2) Return air thermistor configured but not connected | 60 |
| E28 | 1) Supply air thermistor out of bounds 2) Supply air thermistor configured but not connected | 60 |
S9V2-VS codes
The S9V2-VS is a two-stage condensing furnace with a variable-speed draft inducer. Its manual, FNR-SVX001C-EN, has no separate error-code table; the codes are printed in the legend of the S9V2-VS wiring diagram (Figure 3, p. 19, diagram D346055P01 Rev E). Note E06, where the other series split polarity and grounding into E6.1 and E6.2.
| Code | Trane's description (verbatim) | Page |
|---|---|---|
| E01 | Loss of the IRQ/other internal failures | 19 |
| E2.1 | Retry exceeded (Failed to est flame) | 19 |
| E2.2 | Recycles exceeded (loss of established flame) or 10X PS1 open | 19 |
| E2.3 | 1st Stage Gas Valve not energized when it should be exceeded after 10 times | 19 |
| E2.4 | Redundant Relay (HLO output) Not Energized when it should be exceeded after 10 times | 19 |
| E3.1 | Shorted Pressure Switch, 1st Stage | 19 |
| E3.2 | Open Pressure Switch, 1st Stage | 19 |
| E3.3 | Shorted Pressure Switch, 2nd Stage | 19 |
| E3.4 | Open Pressure Switch, 2nd Stage | 19 |
| E04 | Open Thermal Limit, Rollout Switch, or Reverse Airflow Switch | 19 |
| E05 | Flame detected, should not be present | 19 |
| E06 | Voltage reversed polarity or Bad Grounding | 19 |
| E6.3 | (1) Igniter relay fails, (2) Igniter open | 19 |
| E7.1 | 1st stage gas valve (MVL) is energized when it should be off | 19 |
| E7.2 | Redundant Relay (HLO output) Energized when it should NOT be | 19 |
| E08 | Flame current is low, but still strong enough to allow operation. | 19 |
| E09 | Open Inducer Limit Switch or Condensate Switch | 19 |
| E10 | Inducer Motor no communication response, could be communication failure between two micro-controllers. | 19 |
| E11 | (1) 2nd stage gas valve energized when it should NOT be (2) 2nd stage gas valve not energized when it should be (3) 1st stage gas valve not energized when it should be (4) Redundant relay (HLO output) not energized when it should be | 19 |
| E12 | Open fuse | 19 |
| E13 | Blower HP/OEM ID | 19 |
| E14 | No PM and local copy bad | 19 |
| E15 | Both of Unit Data File in PM and local Unit Data File are Corrupt | 19 |
| E17 | Blower motor no communication response | 19 |
| E18 | Blower communication failure on the control | 19 |
American Standard A801X codes
The A801X is American Standard's single-stage induced-draft furnace. Its manual, A801X-SVX001-1D-EN, prints an error-code list on p. 48. It matches the Trane S8X1 list code for code, including the second-stage E11 conditions marked "(Not Applicable for A801X)", but has no E3.3 or E3.4 row.
| Code | American Standard's alarm explanation (verbatim) | Page |
|---|---|---|
| E01 | Loss of the IRQ or other internal failures (Internal IFC error) | 48 |
| E2.1 | Retry Exceeded (Flame never sensed, one hour lockout after 3 times) | 48 |
| E2.2 | Recycles Exceeded (Flame sensed then lost, one hour lockout after 10 times) | 48 |
| E2.3 | 1st Stage Gas Valve Not Energized When It Should Be exceeded after 10 times | 48 |
| E3.1 | Shorted Pressure Switch, 1st Stage | 48 |
| E3.2 | Open Pressure Switch, 1st Stage | 48 |
| E04 | Open Limit (Main Thermal, Rollout Switch, or Reverse Airflow Switch) | 48 |
| E05 | Flame detected, should not be present | 48 |
| E6.1 | Voltage reversed polarity | 48 |
| E6.2 | Bad grounding | 48 |
| E6.3 | (1) Igniter relay fails (2) Igniter open | 48 |
| E7.1 | 1st stage gas valve (MVL) is energized when it should be off | 48 |
| E08 | Flame current is low, but still strong enough to allow operation | 48 |
| E11 | (1) 1st stage gas valve not energized when it should be (2) 1st stage gas valve relay stuck closed (3) 2nd stage gas valve relay stuck closed (Not Applicable for A801X) (4) 2nd stage gas valve energized when it should not be (Not Applicable for A801X) (5) 2nd stage gas valve not energized when it should be (Not Applicable for A801X) | 48 |
| E12 | Open fuse | 48 |
American Standard A951X codes
The A951X is a single-stage condensing furnace. Table 35 of FNR-SVX004B-EN is the shortest list here, with single-stage wording ("Shorted Pressure Switch", "Gas valve") and a different lockout count: E2.1 locks out "after 6 times".
| Code | American Standard's alarm explanation (verbatim) | Page |
|---|---|---|
| E01 | Loss of the IRQ or other internal failures (Internal IFC error) | 76 |
| E2.1 | Retry Exceeded (Flame never sensed, one hour lockout after 6 times) | 76 |
| E2.2 | Recycles Exceeded (Flame sensed then lost, one hour lockout after 10 times) | 76 |
| E2.3 | Gas Valve Not Energized When It Should Be exceeded after 10 times | 76 |
| E3.1 | Shorted Pressure Switch | 76 |
| E3.2 | Open Pressure Switch | 76 |
| E04 | Open Limit (Main Thermal, Rollout Switch, or Reverse Airflow Switch) | 76 |
| E05 | Flame detected, should not be present | 76 |
| E6.1 | Voltage reversed polarity | 76 |
| E6.2 | Bad grounding | 76 |
| E6.3 | (1) Igniter relay fails (2) Igniter open | 76 |
| E7.1 | Gas valve (MVL) is energized when it should be off | 76 |
| E08 | Flame current is low, but still strong enough to allow operation | 76 |
| E09 | Open Inducer Limit Switch or Condensate Pressure Switch | 76 |
| E11 | Gas valve not energized when it should be; Gas valve relay stuck closed | 76 |
| E12 | Open fuse | 76 |
American Standard A952V codes
The A952V is a two-stage condensing variable-speed furnace. Its Table 40 in FNR-SVX005B-EN carries the same blower and memory codes as the Trane S9V2-VS (E10 to E18), with E10 worded differently and polarity and grounding split into E6.1 and E6.2.
| Code | American Standard's alarm explanation (verbatim) | Page |
|---|---|---|
| E01 | Loss of the IRQ or other internal failures (Internal IFC error) | 89 |
| E2.1 | Retry Exceeded (Flame never sensed, one hour lockout after 3 times) | 89 |
| E2.2 | Recycles Exceeded (Flame sensed then lost, one hour lockout after 10 times) | 89 |
| E2.3 | 1st Stage Gas Valve Not Energized When It Should Be exceeded after 10 times | 89 |
| E2.4 | Redundant Relay (HLO output) Not Energized when it should be exceeded after 10 times | 89 |
| E3.1 | Shorted Pressure Switch, 1st Stage | 89 |
| E3.2 | Open Pressure Switch, 1st Stage | 89 |
| E3.3 | Shorted Pressure Switch, 2nd Stage | 89 |
| E3.4 | Open Pressure Switch, 2nd Stage | 89 |
| E04 | Open Limit (Main Thermal, Rollout Switch, or Reverse Airflow Switch) | 89 |
| E05 | Flame detected, should not be present | 89 |
| E6.1 | Voltage reversed polarity | 89 |
| E6.2 | Bad grounding | 89 |
| E6.3 | 1. Igniter relay fails 2. Igniter open | 89 |
| E7.1 | 1st stage gas valve (MVL) is energized when it should be off | 89 |
| E7.2 | Redundant Relay (HLO output) Energized when it should Not be | 89 |
| E08 | Flame current is low, but still strong enough to allow operation | 89 |
| E09 | Open Inducer Limit Switch or Condensate Pressure Switch | 89 |
| E10 | Communication error between variable speed inducer and blower motor microprocessor | 89 |
| E11 | 1. 1st stage gas valve not energized when it should be 2. 1st stage gas valve relay stuck closed 3. 2nd stage gas valve relay stuck closed 4. 2nd stage gas valve energized when it should not be 5. 2nd stage gas valve not energized when it should be | 89 |
| E12 | Open fuse | 89 |
| E13 | Blower HP/OEM ID | 89 |
| E14 | No PM and local copy bad | 89 |
| E15 | Both of unit Data File in PM and local Unit Data File are corrupt | 89 |
| E17 | Blower motor no communication response | 89 |
| E18 | Blower communication failure on the control | 89 |
Older furnaces with a replacement control
Older furnaces fitted with the replacement controls below flash LEDs instead. We did not find their original installation manuals with a code table in Trane's public library, but Trane does publish the guides for the replacement integrated furnace controls (IFC) that service technicians fit to them, and each guide prints the diagnostic table of the control it installs. These are the codes of that replacement control: if your furnace still has its original board, the label on its blower door is the reference. The guides list the furnaces they fit on p. 1 (18-CH111D1-1A-EN on p. 2); 18-CH92D1-1A-EN and 18-CH76D1-1A-EN add the note "* May be "A" or "T"".
- Kit 18109, 18-CH92D1-1A-EN: "*DD---C---A0 up to and including *DD---C---H5 (1990-1999)" and "*DC---C---A0 up to and including *DC---C---B5 (1990-1998)".
- Kit 17399, 18-CH76D1-1A-EN: seven *UD2 models from *UD2B060ACV32A to *UD2D140ACV52A, and four *DD2 models from *DD2B060ACV32A to *DD2D120ACV52A.
- Kit 20350, 18-CH111D1-1A-EN: TUX, TDX, AUX and ADX models such as TUX080R942W5, TDX2B060A9362AB, AUX100R948W6 and ADX120R960W6.
| Green LED flash | Red LED flash | ERROR (LitePort™ DATA), kits 18109 and 20350 (verbatim) | Kit 17399, where different (verbatim) |
|---|---|---|---|
| 1 | NORMAL OPERATION - Flash every 20 seconds | same | |
| 2 | SYSTEM LOCKOUT RETRIES OR RECYCLES EXCEEDED | same | |
| 3 | PRESSURE SWITCH FAULT | same | |
| 4 | OPEN LIMIT SWITCH | same | |
| 5 | FLAME SENSED WHEN NO FLAME SHOULD BE PRESENT | same | |
| 6 | 115 VOLT AC POWER REVERSED OR IMPROPER GROUND | 115 VOLT AC POWER REVERSED OR IGNITER FAULT | |
| 7 | GAS VALVE CIRCUIT ERROR | same | |
| 8 | LOW FLAME SENSE SIGNAL | same | |
| 9 | IGNITER RELAY FAULT | OPEN INDUCER LIMIT | |
| 10 | not listed | COMMUNICATION FAULT | |
| Continuous On | not listed | INTERNAL CONTROL FAILURE | |
| Slow Flash | NORMAL, NO CALL FOR HEAT | same | |
| Fast Flash | NORMAL, CALL FOR HEAT PRESENT | same | |
| Continuous On | Continuous On | INTERNAL CONTROL FAILURE | same |
| Continuous Off | Continuous Off | FUSE OPEN | same |
Same code, different meaning
These are the places where Trane's and American Standard's own documents give one code different wording or a different meaning. Read your own series' table, not the nearest number.
| Code | Where it means one thing | Where it means another |
|---|---|---|
| E2.1 | S9X1/S9X2/S9B1, S8X1/S8X2, A801X, A952V: "one hour lockout after 3 times" | A951X: "after 6 times"; S8V2: "after 7 times"; S9V2-VS: "Retry exceeded (Failed to est flame)", no count |
| E04 | Most series: "Open Limit (Main Thermal, Rollout Switch, or Reverse Airflow Switch)" | S8V2 has no E04; it splits the limit into E4.0 "Open high limit switch", E4.1 "Open reverse air-flow limit switch" and E4.2 "Open roll-out limit switch" |
| E06 / E6.1 / E6.2 | S9V2-VS: E06 "Voltage reversed polarity or Bad Grounding" | Every other current series: E6.1 "Voltage reversed polarity" and E6.2 "Bad grounding" |
| E09 | S9X1/S9X2/S9B1, A951X, A952V: "Open Inducer Limit Switch or Condensate Pressure Switch" | S9V2-VS: "…or Condensate Switch"; not in the S8X1/S8X2, S8V2 or A801X tables |
| E10 | S9V2-VS: "Inducer Motor no communication response, could be communication failure between two micro-controllers." | A952V: "Communication error between variable speed inducer and blower motor microprocessor" |
| E13 | S8V2: "Blower HP or OEM ID do not match furnace" | S9V2-VS, A952V: "Blower HP/OEM ID" |
| E14 | S8V2: "Configuration file error" | S9V2-VS, A952V: "No PM and local copy bad"; S9X1/S9X2/S9B1: "E14 / E18 Refer troubleshooting flow chart" |
| E17 | S8V2: "Blower communication error" | S9V2-VS, A952V: "Blower motor no communication response" |
| 6 red flashes | Kits 18109 and 20350: "115 VOLT AC POWER REVERSED OR IMPROPER GROUND" | Kit 17399: "115 VOLT AC POWER REVERSED OR IGNITER FAULT" |
| 9 red flashes | Kits 18109 and 20350: "IGNITER RELAY FAULT" | Kit 17399: "OPEN INDUCER LIMIT" |
What an owner can do, and what the manuals leave to a servicer
These manuals are written for installers and service technicians. What they say that touches the homeowner is short, and most of it is a warning:
| Task | The manual's wording (verbatim) | Who |
|---|---|---|
| Filters | "Filters should be cleaned or replaced (with high velocity filters only), monthly and more frequently during high use times of the year such as midsummer or midwinter." (FNR-SVX002B-EN, p. 117) | Not stated |
| Blower door | "Verify the blower door is in place and not ajar. Dangerous fumes could escape an improperly secured door." (FNR-SVX002B-EN, p. 3) | Anyone who opens it |
| Burner flame | "accumulation of foreign material may cause a yellowing flame or delayed ignition. Either condition indicates that a service call is required." (FNR-SVX002B-EN, p. 117) | Service call |
| Blower cleaning | "Annual cleaning of the Blower wheel and housing is recommended for maximum air output, and this must be performed only by a qualified servicer or service agency." (FNR-SVX002B-EN, p. 117) | Qualified servicer or service agency |
| Installation and service | "Installation and service must be performed by a qualified installer, service agency, or the gas supplier." (FNR-SVX008A-EN, p. 3) | Qualified installer, service agency or gas supplier |
Everything an error code points at, from pressure switches and limits to igniters, gas valves and the control board, is servicer work. The codes are worth writing down for the technician, including the L6F fault history if the servicer reads it out.
Trane's gas and carbon monoxide wording
The furnace pages on this site carry the general guidance above. This is the manufacturer's own wording, from the safety pages of the current manuals.
| Wording (verbatim) | Source |
|---|---|
| "Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or any other appliance. WHAT TO DO IF YOU SMELL GAS: • Do not try to light any appliance. • Do not touch any electrical switch; do not use any phone in your building. • Immediately call your gas supplier from a neighbor's phone. Follow the gas supplier's instructions. If you cannot reach your gas supplier, call the fire department. • Installation and service must be performed by a qualified installer, service agency, or the gas supplier." | FNR-SVX008A-EN, p. 3 |
| "Install a gas detector for leak warnings. The manufacturer does not test or endorse any specific brand or type of detector." | FNR-SVX008A-EN, p. 3 |
| "Never test for gas leaks with an open flame." | FNR-SVX008A-EN, p. 3 |
| "The U.S. Consumer Product Safety Commission recommends that users of gas-burning appliances install carbon monoxide detectors as well as fire and smoke detectors per the manufactures installation instructions to help alert dwelling occupants of the presence of fire, smoke or unsafe levels of carbon monoxide." | FNR-SVX002B-EN, p. 54 |
| "The installer must verify that at least one carbon monoxide alarm has been installed within the residential living space or home following the alarm manufacturer's instructions and applicable local codes before putting the appliance into operation." | FNR-SVX002B-EN, p. 19 |
| "Carbon Monoxide Poisoning! … Verify the blower door is in place and not ajar. Dangerous fumes could escape an improperly secured door." | FNR-SVX002B-EN, p. 3 |
Trane and American Standard furnaces not covered yet
Trane's public library also holds 2020–2022 revisions of several of these manuals (18-CE12D1-1D-EN for the S9 single and two stage, 18-CE14D1-1A-EN and 18-CE16D1-1C-EN for the S8B1, S8X1 and S8X2, 18-CE03D1-1F-EN and 18-CE19D1-1B-EN for the S9V2) and the American Standard A951X installer's guide 88-A951X001-1D-EN. This page uses the newest revision of each series. The S8B1 appears in the 2020–2021 S8 manuals but not in the October 2026 one, so it is not in the S8X table above.
For older furnaces whose original control is still fitted, we found no original installation manual with a code table in the public library, so this page has no table for them beyond the replacement-control kits.
For other brands' schemes, see the Goodman, Rheem and Carrier furnace code hubs.
Frequently asked questions
What does E2.1 mean on a Trane furnace?
The furnace tried to light and never sensed a flame, then locked out for an hour. On the S9X1, S9X2, S9B1, S8X1 and S8X2 the table reads "Retry Exceeded (Flame never sensed, one hour lockout after 3 times)"; the S8V2 locks out after 7 tries and the American Standard A951X after 6.
What does E04 mean on a Trane or American Standard furnace?
An open limit. Most tables read "Open Limit (Main Thermal, Rollout Switch, or Reverse Airflow Switch)". The S8V2 has no E04: it splits the same idea into E4.0 high limit, E4.1 reverse air-flow limit and E4.2 roll-out limit. A limit or roll-out switch that opens is a call for a qualified servicer.
Why does my Trane furnace display IdL, Ht1 or COF?
Those are status readings, not faults. Trane's S9 manual lists "IDL = Idle, no demand for cooling, heating, or fan", "HT1 = Demand for 1st stage gas heat" and "COF = Demand for continuous fan". An error shows as an E-code that alternates with the status and airflow readings.
My older Trane furnace flashes a red light three times. What does it mean?
On a furnace fitted with one of Trane's replacement controls, three red flashes are "PRESSURE SWITCH FAULT" in all three kit guides. A slow green flash is "NORMAL, NO CALL FOR HEAT" and a fast green flash "NORMAL, CALL FOR HEAT PRESENT". An original board may differ; check the label on the blower door.
Are American Standard furnace codes the same as Trane's?
Often, but not always. The replacement-control guides print one table for models whose prefix "May be "A" or "T"". The current American Standard A801X, A951X and A952V have their own manuals, and the A951X locks out after 6 failed ignitions where most Trane series stop at 3.
How do I reset a Trane furnace lockout?
E2.1 and E2.2 end in a one-hour lockout, and Trane's chart says the "Lockout period is for one hour." We found no homeowner reset procedure in these manuals. A code that returns after the lockout ends needs a qualified servicer.