B0300
HVAC Evaporator Temperature Sensor Circuit
The HVAC controller reports a fault in the evaporator temperature sensor circuit, used to prevent evaporator icing.
- Check engine light: Not always
- Emissions related: No
- Repair difficulty: medium
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.
- Evaporator sensor failureCommon
- Faulty sensor connectorPossible
Parts involved
- Evaporator Temperature Sensor
- Hvac Control Module
B0300 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.