Updated 2026-06-25
Trane Furnace Error Codes & What They Mean
Compiled & reviewed by Nikolai Tsyrenov · Updated 2026-06-25
How do I read Trane furnace error codes?
Trane furnaces show a fault as either a counted red-LED flash pattern on the furnace control board (older, non-communicating models) or as a 'CL2.xxx' alert code on the communicating thermostat (XV/XC/XL/S systems).
How to read Trane furnace codes
Trane furnaces show a fault as either a counted red-LED flash pattern on the furnace control board (older, non-communicating models) or as a 'CL2.xxx' alert code on the communicating thermostat (XV/XC/XL/S systems). On LED boards a slow green flash means normal/no call for heat and a fast green flash a normal call for heat; the red LED counts out the fault number. The flash-code chart is printed inside the furnace's lower access panel — your model's chart is the authoritative reference.
Trane furnace code list
| Code | What it means (tap for fixes) |
|---|---|
| 3 Flashes | Retries or recycles exceeded — the control reached the maximum number of ignition retries or flame recycles and stopped trying to light. |
| 4 Flashes | Inducer or pressure switch error — the draft inducer/pressure switch did not prove proper venting (e.g. the pressure switch failed to close). |
| 5 Flashes | Open limit or rollout switch — a high-temperature limit or flame-rollout safety switch has opened, indicating overheating or flame rollout. |
| 6 Flashes | Flame sensed when no flame should be present — the control detects a flame signal when none should exist. |
| 7 Flashes | Line reverse polarity — the incoming 115V line voltage polarity is reversed (line and neutral swapped) or there is a grounding problem. |
| 8 Flashes | Gas valve circuit error — the control detected a fault in the gas-valve circuit (e.g. open or shorted wiring, or an unexpected valve voltage state). |
| 9 Flashes | Weak flame — the flame-current sense signal is low, indicating a weak or poorly sensed flame. |
| Both LEDs solid on | Fuse open or internal control failure — the board's fuse is open (often from a low-voltage wiring short) or the integrated furnace control has an internal failure. A technician should locate the short before replacing the fuse. |
| CL2.020 / CL2.022 (Recycle / Retry) | Communicating-system alert: burners light and flame is proven, then flame drops out and the control recycles; CL2.022 is the lockout after the maximum recycles/retries. Usually a dirty flame sensor, disturbed flame, or restricted secondary heat exchanger. |
| CL2.026.01 (High Limit) | Communicating-system alert: open high-limit switch — the furnace overheated, typically from low airflow (dirty filter, dirty blower, blocked coil) or a restricted flue. Never bypass the limit switch. |
| CL2.087.00 (Rollout Open) | Communicating-system alert: open flame rollout — flames rolled out of the burner area, a serious combustion/venting problem. Stop using the furnace and call a licensed technician; never reset a rollout switch yourself. |
| CL2.092.00 (Check Fuse) | Communicating-system alert: the 24V control-board fuse is open, usually from a short in the low-voltage field wiring. A technician must find the short before replacing the fuse. |
⚠️ Safety first. Gas furnaces burn fuel and produce combustion gases. If you ever smell gas (a rotten-egg or sulfur odor), hear hissing, or your carbon-monoxide alarm sounds, do not touch light switches, thermostats, or the furnace — leave the home immediately and call your gas utility's emergency line or 911 from outside. Homeowners should limit themselves to simple, safe steps: setting the thermostat, checking and replacing the air filter, confirming the furnace switch and breaker are on, keeping supply registers and return grilles open, and clearing snow, ice, or debris from outdoor vent and intake terminations. Never bypass, jumper, or reset safety switches (limit, flame-rollout, or pressure switches), never open the gas valve or burner compartment, and never attempt combustion, electrical, or control-board repairs yourself. Error codes point toward a problem but are not a substitute for proper diagnosis — when in doubt, turn the system off and call a licensed HVAC technician. Keep working carbon-monoxide detectors on every level of your home.
Trane furnace code FAQ
How do I read the error code on a Trane furnace?
Trane furnaces show a fault as either a counted red-LED flash pattern on the furnace control board (older, non-communicating models) or as a 'CL2.xxx' alert code on the communicating thermostat (XV/XC/XL/S systems).
Where is the diagnostic light on a Trane furnace?
It's on the control board, usually visible through a small sight glass on the lower blower-compartment door. You may need to remove the door panel to read it clearly.
What is the most common Trane furnace code?
3 Flashes — Retries or recycles exceeded — the control reached the maximum number of ignition retries or flame recycles and stopped trying to light.
Other brands
Carrier furnace codesGoodman furnace codesLennox furnace codesRheem furnace codesYork furnace codesHeil furnace codes
Sources: manualslib.com. General information for homeowners — confirm against your furnace's installation manual.