Product Name
$0.00
✅ In Stock
🚚 Ships Today
🔒 OEM Certified
🔄 30-Day Return
Same-day dispatch if ordered by 3PM CST
Free shipping on orders $75+
Check compatibility before ordering
Home > Error Codes > Trane
Every documented Trane furnace error code with causes, fixes, and the parts you may need. Also covers: American Standard.
Slow Flashing (1 per 2 sec)
Normal - No Call for Heat
The furnace is in standby mode. No thermostat demand. The system is operating normally and waiting for a heat call.
DIY check: No action needed. This is the normal idle state.
Fast Flashing (2 per sec)
Normal - Call for Heat Active
The thermostat is calling for heat and the furnace is responding. Normal operating sequence in progress.
DIY check: No action needed if the furnace is producing heat normally.
Continuous ON (solid light)
Control Board Failure
The LED is on continuously without blinking. The control board has an internal failure and cannot operate the furnace.
DIY check: Power cycle the furnace (off for 30 seconds, then on). If the LED stays solid, the control board needs replacement.
Common part needed: Shop Control Board →
Continuous OFF (no light)
No Power to Board
The LED is completely off. No power is reaching the control board.
DIY check: Check: furnace switch is ON, breaker is not tripped, door safety switch is engaged (furnace door fully closed). Check the 3A or 5A fuse on the board. Check the transformer output (should read ~24VAC).
Common part needed: Shop Transformer →
2 Flashes
System Lockout
The furnace has exceeded its maximum number of ignition retries or recycles and has locked out. It will not attempt to restart until manually reset.
DIY check: Power cycle the furnace to clear the lockout. If it locks out again within a few cycles, the underlying ignition problem must be fixed first (usually a flame sensor, igniter, or gas supply issue).
Common part needed: Shop Igniter →
3 Flashes
Pressure Switch Error
The vent pressure switch did not close or reopened during operation. The inducer motor may run but the burners will not ignite.
DIY check: Check: clogged condensate drain (most common on 90%+ units), blocked exhaust vent, cracked pressure hose, weak inducer motor. Clear the condensate trap first.
Common part needed: Shop Pressure Switch →
4 Flashes
Open High Temperature Limit
The high-temperature limit switch has opened due to overheating. The blower may run continuously to cool the heat exchanger.
DIY check: Check air filter (dirty filter is the #1 cause), open all supply registers, check the blower wheel for dust buildup, ensure the A-coil is not iced or dirty.
Common part needed: Shop Fan Motor →
5 Flashes
Flame Sensed Without Gas Valve
The flame sensor is detecting a flame signal when the gas valve should be closed. This could indicate a leaking gas valve (serious safety issue) or a faulty flame sensor.
DIY check: Turn off the furnace and gas supply immediately. Call a licensed technician. Do not attempt to diagnose a potential gas leak yourself.
Common part needed: Shop Gas Valve →
6 Flashes
Power Reversed / Poor Grounding
The 115VAC line and neutral are reversed at the furnace connection, or the furnace does not have a proper ground. This can cause erratic operation and is a shock hazard.
DIY check: Check the outlet or junction box wiring. Hot (black) and neutral (white) may be swapped. Verify with a voltmeter. Also check that the ground wire is properly connected.
7 Flashes
Gas Valve Circuit Error
The control board detected a fault in the gas valve circuit. The gas valve is not responding correctly to the board's commands.
DIY check: Check: gas valve wiring connections, gas valve coil resistance (compare to specs). If the valve is clicking but not opening, it may be stuck internally. Gas valve replacement typically requires a licensed technician.
Common part needed: Shop Gas Valve →
8 Flashes
Low Flame Signal
The flame sensor is detecting a flame but the signal is weak (typically below 1 microamp). The furnace may light but shut down after 10-30 seconds.
DIY check: Clean the flame sensor with fine-grit emery cloth or steel wool. Check the sensor wire for damage or poor connection. If cleaning does not fix it, the sensor or its wire may need replacement.
Common part needed: Shop Flame Sensor →
9 Flashes
High Stage Pressure Switch Error
On two-stage furnaces, the high-fire pressure switch did not close or reopened. The furnace may operate on low fire only.
DIY check: Same checks as 3 flashes but specific to the high-stage switch. Check vent sizing for the high-fire BTU rating. The high-stage switch requires more negative pressure to close.
Common part needed: Shop Pressure Switch →
10 Flashes
Line Polarity / Ground Fault
A ground fault or wiring polarity issue has been detected. Similar to 6 flashes but on some newer Trane models indicates a more specific ground fault condition.
DIY check: Verify proper wiring polarity and ground connection at the furnace. Check for any wires touching the cabinet or chassis.
If the same code keeps coming back after you have addressed the obvious cause (dirty filter, flame sensor, etc.), or if you smell gas, see burn marks, or the furnace will not come out of lockout after a power cycle, call a licensed HVAC technician. Electrical and gas work carries real safety risk.