B0156 code meaning
Sun Load Sensor Circuit
What B0156 means
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.
B0156 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.3 to 1.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of B0156
- Cabin gets too warm in strong sun because the system does not add cooling
- Automatic blower and temperature react only to air temperature
Common causes of B0156
- Most likelySensor plug under the dash top cover loose or damaged after windshield work
- PossiblePhotodiode or electronics in the sun load sensor failed
- Less likelySignal or supply wire shorted or open behind the dashboard
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Sun load sensorHvac control module
What each part of B0156 means
| B | Body system: airbags, seat belts, power seats, lights and climate control. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 56 | The exact fault in that area. |
What to do next
- Note B0156 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about B0156
What does B0156 mean?
B0156 means "Sun Load Sensor Circuit". The publicly available J2012 lists skip B0156, and public carmaker documents do not mention it; the same meaning is covered by code B0305. It is a generic code, so it means the same on every make.
Is it safe to drive with B0156?
B0156 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will B0156 fail an emissions test?
B0156 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is B0156 to fix?
Difficulty: medium. A typical repair takes 0.3 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will B0156 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.