Body, generic

B0250 HVAC Air Temperature Internal Sensor Circuit

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

None of the publicly available J2012 lists contain B0250. On the Saab 9-3 the number marks an actuator fault instead: B0250 06 means the floor door motor circuit is open or grounded, which upsets air distribution, while B0251 01 is the B+ short. Taken by its title, the code is about the cabin temperature sensor, which also has the code B0160. These sensors are NTC elements whose resistance falls as they warm, as HELLA documents for its own air temperature sensor. To measure real cabin air rather than still air behind the dash, TGK's patent US6622924B2 pulls air past the thermistor with a small brushless fan whose rotation is reported on its own pin. If the circuit fails, automatic climate control works with a substitute value and the cabin ends up too warm or too cold.

Likely causes

Sensor plug or wiring behind the dashboard open or shorted to ground
NTC element in the sensor damaged
Aspirator fan seized or its intake grille blocked, so the reading lags behind cabin temperature

Symptoms

  • Automatic climate control holds the wrong cabin temperature
  • Blower speed and outlet temperature no longer adapt as the cabin warms up

Repair estimate

DifficultyEasyDIY possible
Parts and labour€40–220
Time0.3–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

cabin air temperature sensorhvac control module

Related codes

B0160B0255B0164

References: saabwisonline.com, patents.google.com, hella.com.