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Error code reference
Trane Furnace Error Code 4
Open high limit device: furnace overheating or limit switch tripped.
SourceTrane XR95 Furnace - Installation Guide: Gas-Fired Direct Vent Condensingp. 39
Diagnostic procedure
The full 4 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
1
First diagnostic step
Check airflow, filter, and limit switch; verify temperature rise is within rating plate specs.
SourceTrane XR95 Furnace - Installation Guide: Gas-Fired Direct Vent Condensingp. 39
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
2 manuals in the MyPros+ library document this code for Trane furnace.
Models covered by the manuals that document this code
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