OBD-II code · Body
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.
Is it safe to drive with B0255?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyAmbient sensor failure (often behind front grille)
- PossibleWater in connector
Symptoms
- Warning light or symbol related to the affected system
- Comfort or safety function impaired
Repair at a glance
- Difficulty
- Easy
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.2–1 h
- Emissions test
- Usually unaffected
- Parts involved
- Ambient Temperature Sensor, HVAC Control Module
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.