B0255
HVAC Air Temperature External Sensor Circuit
A fault has been detected in the external (ambient) temperature sensor circuit used by the HVAC and instrument cluster.
- Check engine light: Not always
- Emissions related: No
- Repair difficulty: easy
Symptoms
- Warning light or symbol related to the affected system
- Comfort or safety function impaired
Common causes
Ordered by how often each turns out to be the cause.
- Ambient sensor failure (often behind front grille)Common
- Water in connectorPossible
Parts involved
- Ambient Temperature Sensor
- Hvac Control Module
B0255 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.