Trane Furnace Error Code None (TS 1 OPEN)

This fault code means that Temperature Sensor 1 has an open circuit, so the furnace control board is receiving no usable signal from that sensor. The board cannot verify safe operating temperatures without this input and will shut down the furnace as a precaution. The problem is located in the sensor itself, the wiring connecting it, or occasionally in the connector terminals.

Yes, the furnace is designed to stop operating when this fault is active because it cannot safely monitor temperatures without the sensor input. Running a furnace without functional temperature sensing risks undetected overheating. Do not attempt to bypass the sensor or override the lockout, as doing so removes an important layer of protection for both the equipment and your home.

Repair costs vary depending on the cause. If only a wiring repair or connector reconnection is needed, diagnostic labor may be the primary expense, often ranging from $75 to $200. Replacing Temperature Sensor 1 typically adds parts costs on top of labor, bringing the total to a range of $150 to $400 or more. Control board replacement, if required, is the most expensive scenario and can range from $400 to $800 or higher depending on the specific model.

A knowledgeable DIYer can inspect visible wiring and connectors for obvious damage or loose connections, which sometimes resolves the fault without parts. However, testing the sensor with a multimeter and safely accessing internal furnace components requires comfort with electrical diagnostics. If the sensor or control board needs replacement, many homeowners prefer to have a certified HVAC technician handle the repair.

A power reset may temporarily clear the fault code and allow the furnace to attempt a new startup cycle, but the error will return if the underlying sensor or wiring problem is not corrected. Repeated resets without repairs will not fix the issue and may delay finding the root cause. Persistent faults after a reset confirm that a component inspection is necessary.