Lennox Heat Pump Error Code DS2:OFF / DS1:FastFlash

This code indicates a discharge sensor fault. The control board detected that the discharge line temperature sensor is either open (electrically failed) or is reading a value outside the normal temperature range. The fault is only triggered after the condition persists for 90 seconds following compressor startup. The system shuts down to protect the compressor until the issue is resolved.

No. The discharge sensor provides critical overtemperature protection for the compressor. Running the system without a functioning discharge sensor risks undetected overheating, which can cause compressor damage. The heat pump should be kept off until the sensor fault is diagnosed and repaired.

Repair costs vary depending on what component is at fault. A replacement discharge temperature sensor or harness typically runs in the range of $20 to $80 for parts, while a service call including labor generally adds $100 to $250 depending on your location and the technician's rates. If the control board requires replacement, costs can be significantly higher, often in the $300 to $600 range for parts and labor combined.

Begin by checking the resistance of the discharge sensor at pins 1 and 2 on the Yellow wire connector and compare it to the rated specification for the sensor. If the resistance is open or out of range, inspect the harness for breaks or corrosion before replacing the sensor or harness. Also verify that the refrigerant charge and airflow are within normal limits, since actual high discharge temperatures can trigger this fault even with a healthy sensor.

A power reset may temporarily clear the code and allow the unit to attempt a restart, but the fault will return within 90 seconds of compressor operation if the underlying sensor or wiring problem has not been fixed. A reset alone is not a repair and should only be used as part of the diagnostic process.