Body, generic

B0156 Sun Load Sensor Circuit

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

The publicly available J2012 lists skip B0156, and public carmaker documents do not mention it; the same meaning is covered by code B0305. A sun load sensor on top of the dashboard tells automatic climate control how strongly sunlight heats the cabin, so the system can add cooling early. HELLA's solar sensor sits centrally on the dash, measures radiation across different zones and reports over LIN. Patent US6888120B2 uses two light-collecting lenses, each aimed at its own photodiode, to separate driver and passenger sides. GM files this sensor under B0183 instead: in the 2011 Saab 9-5 the HVAC module sets it when the 5 V identifying pulse fails to arrive and then works with zero sun intensity.

Likely causes

Sensor plug under the dash top cover loose or damaged after windscreen work
Photodiode or electronics in the sun load sensor failed
Signal or supply wire shorted or open behind the dashboard

Symptoms

  • Cabin gets too warm in strong sun because the system does not add cooling
  • Automatic blower and temperature react only to air temperature

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–200
Time0.3–1.5 h

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

Parts involved

sun load sensorhvac control module

Related codes

B0162B0305

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