Trane Furnace Error Code None (TS 2 OPEN)

The TS 2 OPEN code means the furnace control board has detected an open circuit in the Temperature Sensor 2 circuit. This sensor is a thermistor that provides temperature feedback to the control board during operation. When the board sees no valid signal from this sensor, it shuts the furnace down as a safety measure. The fault can originate at the sensor itself, the connecting wiring, or the terminal connections.

The furnace shuts down specifically because the control board cannot confirm safe operating temperatures without a valid sensor reading, so the lockout itself is a safety response. Operating the furnace while bypassing this fault would be unsafe. Do not jumper or defeat the sensor circuit as a workaround. Address the underlying wiring or sensor fault before returning the furnace to service.

Resetting the furnace by cycling power may temporarily clear the fault display, but if the underlying open circuit condition still exists, the code will return once the control board polls the sensor again. A reset is not a repair. The sensor circuit must be inspected and the open condition corrected before the fault will stay clear.

Some causes of this fault, such as a disconnected wiring connector, can be addressed by a knowledgeable DIYer who is comfortable working inside furnace cabinets. However, diagnosing the difference between a failed sensor, broken wire, and a board-level fault requires a multimeter and some electrical knowledge. If you are not comfortable testing components or tracing wiring, a qualified HVAC technician is the safer choice.

Repair costs depend on the root cause. If only a wiring connector needs reseating, the cost may be limited to a service call fee, typically in the range of $75 to $150. A replacement thermistor sensor usually costs between $20 and $80 in parts, with labor on top of that. Control board replacement, if required, can range from $250 to $600 or more depending on the model.