Code Definition

B1255 — Air Temperature External Sensor Circuit Open

System: Body  |  Type: Manufacturer-Specific  |  Make: Generic

About B1255

B1255 is a manufacturer-specific body diagnostic trouble code. It belongs to the B-prefix family of codes, which covers body, interior, airbag, or comfort-electronics faults.

When B1255 is stored, the module has detected an open (broken or disconnected) electrical path in the monitored circuit; and a sensor-related fault — the reported value from the named sensor is out of spec.

Scanning & clearing: Body (B) codes are often stored in the body control module, airbag module, or climate module. A basic OBD-II tool usually will not read body codes — an enhanced or OEM-level scan tool is typically required.

B1255 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

The external air temperature sensor, also known as the ambient air temperature sensor, is typically mounted behind the front grille, inside the front bumper cover, or under an exterior mirror, where it can measure true outside air temperature without heat soak from the engine bay. It is a negative temperature coefficient (NTC) thermistor whose resistance drops as temperature rises, returning a variable voltage to the climate control module over a two wire circuit (signal and ground). DTC B1255 is set specifically when the climate control module sees the sensor signal voltage pulled up to the f...

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