Error code reference

Lennox Heat Pump Error Code DS2 Simultaneous FAST Flash / DS1 Simultaneous FAST Flash

Ambient sensor problem: sensor detected open, shorted, or out of temperature range; control reverts to time/temperature defrost operation.

SourceLennox 14HPX Series Heat Pump - Service Manual (1.5-5 Ton)p. 10

Lennox codes Lennox heat pump codes

Diagnostic procedure

The full DS2 Simultaneous FAST Flash / DS1 Simultaneous FAST Flash procedure

Step 1 is visible so you can confirm you are on the right page. The remaining steps, the ones that tell you whether to actually replace a part, unlock with any pass.

MyPros+ · DiagnosticsStep 1 preview

First diagnostic step

Check ambient sensor resistance across pins 3 & 4 (Black wires); replace sensor harness if open or shorted.

SourceLennox 14HPX Series Heat Pump - Service Manual (1.5-5 Ton)p. 10

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More steps, wiring diagram references, and verified part numbers

Includes expected resistance and voltage values, connector pinouts, and supersession notes for replacement parts.

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Where this code is documented

1 manual in the MyPros+ library documents this code for Lennox heat pump.

Models covered by the manuals that document this code

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The full DS2 Simultaneous FAST Flash / DS1 Simultaneous FAST Flash procedure

Where this code is documented

Models covered by the manuals that document this code

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