Trane Furnaces Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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1 Flash
Status LED flashes once repeatedly; furnace will not start heating cycle.
Ignition Failure / Lockout
2 Flashes
Status LED flashes twice repeatedly, furnace will not run, inducer may not start.
Pressure Switch Stuck Closed
3 Flashes
Status LED flashes three times repeatedly, inducer runs but burners do not light.
Pressure Switch Stuck Open
4 Flashes
Status LED flashes four times repeatedly, furnace starts but shuts down shortly after ignition.
Open High Limit Switch
5 Flashes
Status LED flashes five times repeatedly, furnace will not start heating cycle.
Flame Sensed With Gas Valve Off (False Flame Signal)
6 Flashes
Status LED flashes six times repeatedly, furnace shuts down and may lock out.
Flame Loss During Run
7 Flashes
Status LED flashes seven times repeatedly, furnace will not start heating cycle.
Gas Valve Circuit Fault
8 Flashes
Status LED flashes eight times repeatedly, furnace may start but shuts down quickly.
Low Flame Sense Signal
9 Flashes
Status LED flashes nine times repeatedly, furnace will not operate.
Reversed Line Polarity or Ground Fault
Blinking Off (No LED)
No LED light, furnace completely dead.
No Power to Furnace
Continuous Fast Flash
Status LED flashes rapidly without pause, furnace does not respond to thermostat.
Incorrect 24V Phase / Low Voltage Polarity
Err 1
Trane communicating furnace control displays 'Err 1' on the ComfortLink II or communicating thermostat.
Communication Error Between Thermostat and Furnace
Err 2
Trane communicating thermostat shows 'Err 2'; furnace may not respond.
Outdoor Unit Communication Fault (in dual fuel or integrated systems)
Err 3
Trane communicating thermostat shows 'Err 3'; furnace may shut down.
Indoor Temperature Sensor Fault
Err 4
Trane communicating thermostat shows 'Err 4'; furnace may not operate correctly.
Outdoor Temperature Sensor Fault (for dual fuel or outdoor sensor-equipped systems)
Err 5
Trane communicating thermostat shows 'Err 5'; system may lock out certain modes.
Configuration or Component Mismatch Error
HARD LOCKOUT
Control indicates hard lockout; furnace will not attempt ignition until reset.
Repeated Ignition Failure Lockout
SOFT LOCKOUT
Control indicates soft lockout; furnace pauses operation for a timed period, then retries.
Temporary Ignition or Flame Sensing Lockout
Steady On
Status LED solid on with no flashing, furnace not responding or stuck.
Normal Power / No Call or Control Board Locked
Symptom
A burning or electrical smell when the furnace runs.
Overheating Components or Electrical Fault
Symptom
Furnace cycles on and off with loud clicking from the control area, but the burners do not stay lit.
Control Board or Relay Malfunction
Symptom
Furnace runs, but the house does not reach the set temperature, resulting in long run times.
Insufficient Heat Output
Symptom
Furnace will not start at all: no blower, no inducer, even with the thermostat calling for heat.
Complete Power Loss to Furnace
Symptom
The furnace blower runs continuously even when the thermostat is not calling for heat or fan.
Blower Stuck in Continuous Operation
Symptom
The furnace blower starts, but there is no warm air, and the burners never ignite.
No Heat / Blower Only Operation
Symptom
The furnace emits a strong gas smell when attempting to start.
Gas Leak or Incomplete Ignition
Symptom
The furnace frequently trips the household circuit breaker.
Electrical Overload or Short Circuit
Symptom
The furnace ignites but produces yellow, lazy flames instead of blue.
Improper Combustion
Symptom
The furnace inducer runs continuously, but the burners do not light.
Draft Proving / Pressure Switch Problem
Symptom
The furnace makes a loud banging or booming noise at startup.
Delayed Ignition
Symptom
The furnace produces a high-pitched squealing noise during operation.
Blower Motor or Belt Noise
Symptom
The furnace rattles or vibrates loudly when running.
Cabinet or Duct Vibration
Symptom
The furnace runs, but airflow from the registers is weak.
Low Airflow
Symptom
The furnace short cycles, turning on and off frequently without reaching the set temperature.
Short Cycling
Symptom
The furnace starts and runs but shuts off after a few minutes, then restarts after cooling.
Overheating / High Limit Cycling
Symptom
The furnace starts but shuts down immediately when the blower starts.
Blower-Induced Flame Disturbance or Limit Trip
Symptom
The thermostat display is blank, and the furnace does not run.
Loss of 24V Control Power
Symptom
Thermostat calls for heat, but the furnace inducer starts and then shuts off without ignition.
Failed Ignition Sequence
Symptom
Water dripping from PVC vent pipe joints or around the exhaust outlet.
Condensate in Vent Piping
Symptom
Water leaking around the base of a high-efficiency Trane furnace.
Condensate Leak
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| 1 Flash |
Status LED flashes once repeatedly; furnace will not start heating cycle.
|
Ignition Failure / Lockout | View Details |
| 2 Flashes |
Status LED flashes twice repeatedly, furnace will not run, inducer may not start.
|
Pressure Switch Stuck Closed | View Details |
| 3 Flashes |
Status LED flashes three times repeatedly, inducer runs but burners do not light.
|
Pressure Switch Stuck Open | View Details |
| 4 Flashes |
Status LED flashes four times repeatedly, furnace starts but shuts down shortly after ignition.
|
Open High Limit Switch | View Details |
| 5 Flashes |
Status LED flashes five times repeatedly, furnace will not start heating cycle.
|
Flame Sensed With Gas Valve Off (False Flame Signal) | View Details |
| 6 Flashes |
Status LED flashes six times repeatedly, furnace shuts down and may lock out.
|
Flame Loss During Run | View Details |
| 7 Flashes |
Status LED flashes seven times repeatedly, furnace will not start heating cycle.
|
Gas Valve Circuit Fault | View Details |
| 8 Flashes |
Status LED flashes eight times repeatedly, furnace may start but shuts down quickly.
|
Low Flame Sense Signal | View Details |
| 9 Flashes |
Status LED flashes nine times repeatedly, furnace will not operate.
|
Reversed Line Polarity or Ground Fault | View Details |
| Blinking Off (No LED) |
No LED light, furnace completely dead.
|
No Power to Furnace | View Details |
| Continuous Fast Flash |
Status LED flashes rapidly without pause, furnace does not respond to thermostat.
|
Incorrect 24V Phase / Low Voltage Polarity | View Details |
| Err 1 |
Trane communicating furnace control displays 'Err 1' on the ComfortLink II or communicating thermostat.
|
Communication Error Between Thermostat and Furnace | View Details |
| Err 2 |
Trane communicating thermostat shows 'Err 2'; furnace may not respond.
|
Outdoor Unit Communication Fault (in dual fuel or integrated systems) | View Details |
| Err 3 |
Trane communicating thermostat shows 'Err 3'; furnace may shut down.
|
Indoor Temperature Sensor Fault | View Details |
| Err 4 |
Trane communicating thermostat shows 'Err 4'; furnace may not operate correctly.
|
Outdoor Temperature Sensor Fault (for dual fuel or outdoor sensor-equipped systems) | View Details |
| Err 5 |
Trane communicating thermostat shows 'Err 5'; system may lock out certain modes.
|
Configuration or Component Mismatch Error | View Details |
| HARD LOCKOUT |
Control indicates hard lockout; furnace will not attempt ignition until reset.
|
Repeated Ignition Failure Lockout | View Details |
| SOFT LOCKOUT |
Control indicates soft lockout; furnace pauses operation for a timed period, then retries.
|
Temporary Ignition or Flame Sensing Lockout | View Details |
| Steady On |
Status LED solid on with no flashing, furnace not responding or stuck.
|
Normal Power / No Call or Control Board Locked | View Details |
| – |
A burning or electrical smell when the furnace runs.
|
Overheating Components or Electrical Fault | View Details |
| – |
Furnace cycles on and off with loud clicking from the control area, but the burners do not stay lit.
|
Control Board or Relay Malfunction | View Details |
| – |
Furnace runs, but the house does not reach the set temperature, resulting in long run times.
|
Insufficient Heat Output | View Details |
| – |
Furnace will not start at all: no blower, no inducer, even with the thermostat calling for heat.
|
Complete Power Loss to Furnace | View Details |
| – |
The furnace blower runs continuously even when the thermostat is not calling for heat or fan.
|
Blower Stuck in Continuous Operation | View Details |
| – |
The furnace blower starts, but there is no warm air, and the burners never ignite.
|
No Heat / Blower Only Operation | View Details |
| – |
The furnace emits a strong gas smell when attempting to start.
|
Gas Leak or Incomplete Ignition | View Details |
| – |
The furnace frequently trips the household circuit breaker.
|
Electrical Overload or Short Circuit | View Details |
| – |
The furnace ignites but produces yellow, lazy flames instead of blue.
|
Improper Combustion | View Details |
| – |
The furnace inducer runs continuously, but the burners do not light.
|
Draft Proving / Pressure Switch Problem | View Details |
| – |
The furnace makes a loud banging or booming noise at startup.
|
Delayed Ignition | View Details |
| – |
The furnace produces a high-pitched squealing noise during operation.
|
Blower Motor or Belt Noise | View Details |
| – |
The furnace rattles or vibrates loudly when running.
|
Cabinet or Duct Vibration | View Details |
| – |
The furnace runs, but airflow from the registers is weak.
|
Low Airflow | View Details |
| – |
The furnace short cycles, turning on and off frequently without reaching the set temperature.
|
Short Cycling | View Details |
| – |
The furnace starts and runs but shuts off after a few minutes, then restarts after cooling.
|
Overheating / High Limit Cycling | View Details |
| – |
The furnace starts but shuts down immediately when the blower starts.
|
Blower-Induced Flame Disturbance or Limit Trip | View Details |
| – |
The thermostat display is blank, and the furnace does not run.
|
Loss of 24V Control Power | View Details |
| – |
Thermostat calls for heat, but the furnace inducer starts and then shuts off without ignition.
|
Failed Ignition Sequence | View Details |
| – |
Water dripping from PVC vent pipe joints or around the exhaust outlet.
|
Condensate in Vent Piping | View Details |
| – |
Water leaking around the base of a high-efficiency Trane furnace.
|
Condensate Leak | View Details |
No matching codes found
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