Trane Furnace Error Code Green OFF / Red Flashing

This status code means the ignition control module locked out after the furnace failed to establish a confirmed flame signal during the ignition sequence. The module attempted to light the burners, did not receive an acceptable signal from the flame sensor within the allowed time, and shut down all ignition activity as a safety precaution. No heat will be produced until the lockout is cleared and the underlying cause is corrected.

Resetting the furnace once or twice to confirm the fault is repeatable is reasonable, but repeatedly resetting without diagnosing the cause is not advisable. The lockout function exists to prevent unburned gas from accumulating, and bypassing it without addressing the underlying issue could create a hazardous situation. If the furnace locks out again after a reset, shut it down and arrange for a qualified technician to inspect the ignition system before continuing to operate the unit.

Repair costs vary depending on the failed component. Flame sensor cleaning is often a low-cost service call in the range of $80 to $150 if no parts are needed. Replacing a hot surface igniter typically costs between $100 and $250 including labor. A gas valve replacement is more involved and can range from $200 to $500 or more depending on labor rates and the specific valve required. Diagnosing the cause accurately before ordering parts helps avoid unnecessary expense.

You can reset the lockout by switching off the equipment disconnect switch, waiting a few seconds, and turning it back on. Alternatively, turning the thermostat or zone sensor to the OFF position and then back to heating mode will also clear the lockout. The control module will also auto-reset on its own after approximately one hour without any manual intervention. Keep in mind that if the root cause is not fixed, the furnace will lock out again after the next failed ignition attempt.

A reset clears the lockout state and allows the furnace to attempt ignition again, but it does not fix the underlying problem. If the flame sensor is dirty, the igniter is failing, or there is a gas supply issue, the furnace will go through its ignition sequence, fail again, and return to lockout. A lasting fix requires identifying and correcting the specific component or condition that is preventing successful flame establishment.