Trane Furnace Error Codes List: Every Code Explained

Every Trane furnace error code we could verify against Trane's own documentation — what it means, what usually causes it, and the first fix to try — in one table. Codes differ between model series, so treat your model's tech sheet as the final word.

How to read and retrieve error codes on Trane furnaces

Trane boards provide the fault history through the LED pattern and, on communicating models, through the thermostat's installer menu, which lists stored alert codes (the alphanumeric family). The fault chart on the blower door is the authority for your unit — Trane changed flash-pattern assignments between generations, and charts copied between websites frequently mix them up.

The complete Trane furnace error code list

How to reset / clear error codes on Trane furnaces

Trane furnaces report faults as red-LED flash patterns on the control board (count the flashes between pauses) on non-communicating models, and as alphanumeric codes on communicating/XV models. Soft lockouts retry automatically; hard lockouts clear by fixing the cause and cycling power at the furnace switch. The board stores recent faults — on many models the LED keeps the last fault flash pattern available until the next successful cycle overwrites it.

How to diagnose any Trane furnace code

Work the problem in this order — and stop at any point where gas, combustion or mains wiring is involved, because those belong to a licensed HVAC technician: (1) record the code exactly: count LED flashes slowly, twice, or photograph the alphanumeric display; (2) check the free things homeowners legitimately own: the thermostat is calling for heat, the furnace power switch and breaker are on, the filter is not clogged solid (a starved furnace overheats and locks out on limit codes), all vents and the return are open, and the condensate drain is not blocked on condensing models; (3) reset once — at the power switch, off for 30 seconds — then watch a full call for heat from the beginning: inducer, ignition, flame, blower, in that order; where the sequence stops is the fault family the code names; (4) a code that returns immediately is an active fault — do not keep resetting a lockout, especially any flame or limit code; (5) everything inside the burner compartment — flame sensor cleaning is the one grey area many manuals allow owners, but gas valves, burners, heat exchangers and control boards are professional work. If you smell gas at any point, leave and call the gas utility, not a helpline.

Flash counts on older boards, E-codes on communicating furnaces

Trane furnaces report faults two ways depending on generation. The integrated furnace control on most models flashes a red LED in counted patterns, read against the fault chart printed in the installation manual and on the unit — that chart, for your exact model, is the authority. Trane's communicating and modulating furnaces (the S-series and XV generation) instead show alphanumeric E-codes on a display and store a fault history. The table below covers both dialects and keys each entry the way Trane displays it, because a "4 flashes" fault and an E-code with a similar number are unrelated reports.

Lockouts are the furnace protecting itself, not a second fault

After repeated failed attempts at the same step — ignition above all — a Trane control stops trying and locks out for a period rather than cycling forever against a fault that could overheat the furnace or flood the burners with unburned gas. A lockout is evidence, not damage: it tells you the same step failed repeatedly. Reset once, at the power switch, and watch one full call for heat from the start — inducer, pressure proof, ignition, flame, blower — because where the sequence stops is the fault family. A code that returns immediately is an active fault; do not keep resetting it, and leave everything inside the burner compartment to a licensed HVAC technician.

Blink codes, display codes and lockouts

Two generations of fault reporting live side by side on modern furnaces. Older and simpler boards report through a single LED: a repeating count of flashes, read slowly against the chart printed inside the blower door — that chart, for your exact model, outranks any list on the internet, including this one. Newer communicating furnaces show alphanumeric codes (the E-series in the table above) and store a fault history a technician can scroll. Both generations share the lockout idea: after a set number of failed attempts at the same step — ignition is the classic — the board stops trying for a period (often an hour, or until power is cycled) instead of cycling forever against a fault that could overheat or flood the burners with unburned gas. A furnace in lockout is not broken by the lockout itself; it is a furnace that has already failed the same step repeatedly and is waiting for someone to find out why.

Furnace codes are also seasonal in a way washer codes are not. The first cold snap produces a wave of ignition and flame codes from furnaces that sat idle all summer — oxidised flame sensors, spider-nested burners, pressure-switch hoses holding condensate from the cooling season. Deep-winter adds frozen condensate lines on high-efficiency models and intake/exhaust terminations blocked by snow or ice, which present as pressure-switch codes. A code that appears once, on the coldest night of the year, and never again has often met its cause already; a code that appears every cycle, in any weather, is a component asking to be tested.

The most searched Trane furnace codes, in detail

E09 — Not a Trane-published furnace code

This is the page we publish when a code cannot be verified, and the reasoning is worth showing. Trane's own consumer guidance on furnace codes (its blinking-light troubleshooting page) teaches homeowners to count LED flashes and write codes down exactly, and warns against DIY furnace repair — but it never lists an E09. Trane's published ignition diagnostics (Trane's support knowledge base, covering its ignition controller boards) define the furnace fault language as flash counts: 2 flashes for system lockout, 3 for a pressure switch problem, 4 for an open high limit, 5 for flame sensed with the gas valve off, 6 for an open rollout, and so on. On Trane's communicating systems, alerts surface on the thermostat in worded or formally numbered formats (the ERR and CFG families on ComfortLink controls), again not as a bare E09. And when Trane Home's own support is asked about codes, its published answer is blunt: Trane Home Support cannot decipher error codes, and questions about their meanings go to your HVAC dealer. Against that silence, third-party websites confidently define E09 — and disagree with each other, some calling it a pressure-switch fault, others a communication or sensor fault. Mutually contradictory definitions with no manufacturer document behind any of them are the fingerprint of a code being guessed at. The honest summary: some Trane-family boards do show character displays, and an E09 seen on one can only be decoded by that model's own rating-plate documentation or door chart — not by the internet's consensus.

Most likely cause: A model-specific display code with a dealer-only decode — The most likely truth behind most E09 reports: display-equipped Trane platforms can generate codes that Trane documents in installer and dealer literature rather than in anything published for homeowners. The code is real to the board that posted it — it simply has no public Trane definition, which is a documentation gap, not permission to borrow one from another brand or site.

First check: Photograph the display showing E09 and write the characters down exactly, including anything before or after them — the full string, not the memorable part of it.

If it keeps coming back: An undefined code 'keeps coming back' for the simplest of reasons: the condition behind it was never identified, so it was never fixed. Every E09 that survives a power cycle should escalate the documentation hunt — exact string, model number, door chart, dealer decode — rather than another round of resets or a part bought against a guessed meaning.

3 Flashes — Pressure switch fault

On Trane's blink-code furnaces, 3 flashes is the pressure-switch family: the inducer ran but the switch didn't prove draft (on many Trane charts, 3 flashes covers pressure switch stuck open/closed variants — the chart inside the blower door is the authority for your exact model). The diagnosis is the universal pressure-switch chain: vent/intake blockage (snow and nests lead), condensate trap/drain on condensing models, the switch's tubing (cracked or water-filled), inducer strength, and the switch itself last. Trane's own wording for this code is worth having exactly, because it names three different problems under one flash count. In Trane's published ignition-controller diagnostics, the entry reads: "3 Flashes — Pressure switch problem detected (no vent air flow, bad CBM, closed at an initial call for heat). Auto reset." Read the brackets as a branch list. Branch one, no vent air flow: the inducer runs but cannot move enough air — or pull enough vacuum — for the switch to prove the vent path. Branch two, the switch was already closed at the initial call for heat: the board checks the switch before the inducer starts, finds proof it has not earned yet, and aborts the sequence immediately rather than firing on a switch it cannot trust. Branch three is the control itself (the board Trane abbreviates as the CBM in that table). All three report identically — three flashes, no ignition — which is why the observed sequence matters so much: a code that appears before the inducer even starts is branch two or three talking, while a code that arrives after the inducer has run points at the airflow branch. The same Trane table closes with the behaviour owners ask about most: this fault is an auto reset, so the board will try again on the next call once the condition clears, with no manual reset ritual required or published.

Most likely cause: Blocked vent/intake — Snow, ice, nests — the winter classic.

First check: SAFETY: never jumper a pressure switch to 'test' heating — it proves exhaust can leave.

If it keeps coming back: Cold-snap recurrence = termination icing or a freezing condensate line; rainy-day recurrence = vent water/sag. The returns of this code tend to follow the weather and the water. Inducer and vent proofs that pass in mild weather fail on the coldest nights, when a frost-narrowed termination or a sluggish condensate drain steals the last of the vacuum margin; condensate branches return whenever the trap or tube re-fills faster than it drains. A 3-flash pattern that clusters at night or in cold snaps is telling you the margin — not the switch — is the disease, and it is why a technician who only swaps the switch often gets the same callback Trane's branch list was written to prevent.

5 Flashes — Flame sensed when no flame should be present

A furnace control spends its whole life asking one question in two directions: during a burn, 'is the flame really there?' — and at every other moment, 'is the flame really gone?' Five flashes is the second question failing. The control is receiving a flame-proving signal (the flame sensor works by flame rectification: a real flame conducts a tiny DC current between the sensor rod and the burner, and the control reads that current as proof) while the gas valve is de-energised — at standby, before ignition, or after a cycle that should have ended clean. Only three physical stories produce that signal, and Trane's verified chart names them: a leaking or stuck gas valve keeping a real flame alive on gas it should be holding back; a lingering burner flame that has not gone out when it should; or a fault in the flame sensing circuit itself, where the signal is false — Trane's display-generation wording for the same fault (code E05 on S-series/A801X controls) lists a shorted flame sense wire or a grounded flame sensor alongside the leaking valve. The control's response is not negotiable and not a glitch to be cleared: flame out of sequence is among the most serious reports a furnace can make, because each branch is bad in a different way — uncommanded gas burning, or a safeguard that can no longer be believed. If the sensor lies in the 'flame present' direction today, nothing guarantees its honesty in the other direction tomorrow. That is why the verified fix for 5 flashes begins with turning the furnace off, and why this page will not offer a reset-and-run path: the furnace stays off until a technician has established which of the three stories is true. Note the contrast with 8 flashes (low flame sense signal): that is a weak-but-honest signal during a legitimate burn — a cleaning-and-measurement job. Five flashes is a signal at a forbidden time, and forbidden beats weak in every safety hierarchy.

Most likely cause: Leaking gas valve — Trane's lead cause: the valve passes gas with its solenoid de-energised, so a flame — even a small, lazy one at one burner port — persists or re-establishes after the cycle should have ended. The flame the sensor reports is real; it is the valve's shutoff that is fictional. This branch is a gas-safety fault, not a controls nuisance.

First check: SAFETY OVERRIDES EVERY OTHER STEP: if you smell gas, turn the furnace off, shut off gas at the furnace's manual valve if you know where it is, leave the house if the smell is strong, and call your gas utility or a licensed HVAC technician. Never attempt to bypass, disconnect or defeat the flame sensor to get heat — the sensor is the safeguard this code is about.

If it keeps coming back: Five flashes returning after a gas valve replacement, with the new valve proven tight, walks the diagnosis into the sensing chain — wiring shorting intermittently under vibration or heat, a sensor grounding only when hot, or the control's sense circuit drifting. Returns that cluster at the end of cycles keep pointing at flame behaviour (burners, carryover, residual gas); returns at cold power-up keep pointing at the signal. The timing pattern is the diagnosis — record it rather than resetting it away.

7 Flashes — Gas valve circuit error

Where 5 flashes reports what the flame sensor sees, 7 flashes reports what the control knows about its own wiring. The integrated furnace control continuously supervises the gas valve circuit — the output it switches, the harness that carries it, and the valve's solenoid coil at the end of it — and 7 flashes is that supervision failing: the circuit is shorted, open, or drawing or answering in a way the control cannot accept. Trane's verified chart gives the three suspects without ornament: shorted or open gas valve wiring, a failed gas valve coil, or a control board gas valve output fault. Trane's display generation splits this one IFC bucket into the branches the LED chart cannot express, and the split is worth knowing because it shows what 'circuit error' contains: E2.3 is the first-stage gas valve not energised when it should be (ten times within one call for heat); E7.1 is its dangerous mirror — the gas valve energised when it should be off, from a stuck relay or shorted wiring holding the valve on; and E11 is the gas valve fault group that gathers both directions. The LED generation wraps all of that into 7 flashes, so the code by itself does not say whether your furnace cannot open its valve (the common, merely cold outcome: the sequence runs, the igniter may glow, and ignition never happens because the valve is never truly powered) or cannot be trusted to keep it closed (the rare, dangerous outcome the E7.1 branch describes). Either way the control refuses to run a heating cycle on a valve circuit it cannot vouch for, and either way the diagnosis is measurement, not observation: coil resistance, voltage at the valve during the ignition window, and continuity of the harness separate the three suspects in an order no amount of power-cycling can imitate. Note what 7 flashes is not: a gas supply problem. A closed manual valve or an empty street main starves a healthy circuit and produces ignition failure and eventually a 2-flash lockout — the valve was commanded and answered, the flame simply never came. Seven flashes means the command path itself failed its check.

Most likely cause: Shorted gas valve wiring — Trane's first suspect: the harness between control and valve shorted — chafed insulation against the cabinet, a pinched run, or heat-damaged conductors — so the control's valve output sees a load or a path it should not. A short in this circuit is also the branch that can hold a valve energised, which is why the code is treated as a safety report and not a mere no-heat nuisance.

First check: SAFETY: this is a gas valve circuit fault. If you smell gas, furnace off, gas off at the manual valve if you know it, and call your utility or a technician. Never jumper the gas valve, never apply power to the valve manually to test it, and never bypass the control to force a heating cycle — those are precisely the acts this code exists to prevent.

If it keeps coming back: A 7-flash that returns weeks after a repair, especially intermittently, is usually the harness branch maturing: a chafe that only shorts when the cabinet vibrates under the inducer, or a connector pin that loses contact as it heats. Intermittence is itself the clue — log when it faults (cold start, mid-cycle, after other work nearby) rather than resetting the evidence away. Returns immediately after a valve or control replacement mean the unproven half of the pair: the part that was not changed was the guilty one, and the measurement sequence, done fully this time, settles it.

Less common and model-specific codes

Search data shows owners also meet these codes on Trane furnaces: 7P1, E2, E24, E3, E4, E6, Fixes, HE1, HE2. They are not part of the core code list Trane publishes for most models — several are series-specific, abbreviated display readings, or codes carried over from a sister platform — so we do not publish meanings for them rather than guess. Treat them by symptom: note what the machine was doing when the code appeared (filling, draining, heating, spinning), run one full power cycle (5 minutes off), and if the code returns, match the symptom to the closest documented family in the table above and check the tech sheet stored inside your machine for the model-specific definition.

Deep-dive guides for the most searched codes

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Facts on this page were checked against manufacturer documentation: manuals.plus · manuals.plus · manuals.plus · manuals.plus · www.nee.ca · springhome.ca