Error code reference
Lennox Heat Pump Error Code DS2:OFF / DS1:FastFlash
Discharge sensor fault
Discharge sensor fault — open sensor or out-of-temperature sensor range detected after 90 seconds of compressor operation.
First step from the service manual
Check discharge sensor resistance at pins 1 & 2 (Yellow wire); replace sensor harness if not within range.
The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.
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Get the full diagnostic procedure for DS2:OFF / DS1:FastFlash.
- Step-by-step tests with expected resistance, voltage, and continuity values
- Wiring diagram references and connector pinouts from the OEM service manual
- Verified part numbers when replacement is required
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