B0159 B0xxx · Body (B) Low severity
Outside Air Temperature Sensor Circuit
The ambient temperature sensor is open, shorted or reading implausibly. Automatic climate control and some driver displays depend on it.
Severity guidance: Low — usually no drivability impact, fix at the next service
Symptoms you will notice
- Outside temperature display wrong or blank
- Climate control behaves oddly
- Ice warning unreliable
Common causes
Ordered from most to least likely — start at the top.
- 1 Failed sensor (usually in the mirror or front bumper)
- 2 Corroded connector
- 3 Rodent damage to the wiring
- 4 Sensor exposed to heat soak
How to diagnose it
Cheapest and least invasive first — most of these codes are not a parts problem.
- ✓ Compare the displayed value with reality on a cold start.
- ✓ Locate the sensor (mirror housing, grille or bumper) and inspect the wiring.
- ✓ Measure resistance and compare with the temperature table.
Repair options
- Replace the ambient temperature sensor
- Repair the wiring
B0159 — frequently asked questions
The reading is high in traffic — is it broken? +
Heat soak near the radiator is normal. If it stays wrong at speed after a cold soak, the sensor is faulty.
Does it affect engine management? +
Rarely on petrol; some diesel and hybrid strategies use it for aftertreatment or battery thermal logic.
Confirm the diagnosis before you buy parts
Send us the code, freeze-frame data and the vehicle — our engineers will tell you what to test first.