Error code reference

Trane Furnace Error Code 4 Flash

High temperature limit fault - open high limit (heat exchanger temperature too high, possibly caused by low airflow or fan failure), auxiliary limit (reverse flow), or rollout switch open.

SourceTrane XC80 Furnace - Service Manual: Variable Speed 2-Stagep. 30, 41-42

Trane codes Trane furnace codes

Diagnostic procedure

The full 4 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

Scroll User Interface to view Last 4 Faults to determine HIGH LIMIT, AUX LIMIT, or ROLLOUT OPEN; disconnect power and check filter/blower wheel cleanliness.

SourceTrane XC80 Furnace - Service Manual: Variable Speed 2-Stagep. 30, 41-42

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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

3 manuals in the MyPros+ library document this code for Trane furnace.

Models covered by the manuals that document this code

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The full 4 Flash procedure

Where this code is documented

Models covered by the manuals that document this code

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