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Error code reference

Bosch Heat Pump Error Code AtL

Ambient temperature limited condition-ambient temperature beyond operating range, incorrect O/B thermostat setting, or T4 sensor fault.

SourceBosch IDS 2.0 Split System Heat Pump - Full Service ManualSection 12.3.18, page 59

Bosch codesBosch heat pump codes
Diagnostic procedure

The full AtL 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 if ambient temperature is beyond operating range (Cooling: 15-125°F, Heating: -4-86°F).

SourceBosch IDS 2.0 Split System Heat Pump - Full Service ManualSection 12.3.18, page 59

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Where this code is documented

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

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