HVAC Internal Air Temp Sensor Circuit Fault
This manufacturer-specific diagnostic trouble code indicates that the HVAC control module has detected a fault in the circuit of the in-car temperature sensor. This sensor, typically located in the dashboard or integrated into the front control module, measures the cabin's ambient temperature and sends a variable voltage signal to the HVAC module. The code sets when the module identifies an open circuit, a short to ground or power, or a reading outside the calibrated range, preventing automatic temperature regulation.
1. Commonly Affected Makes
2. Most Common Causes
- Faulty or disconnected in-car temperature sensor
- Short or open circuit in the wiring between the sensor and HVAC module
- Corroded connector, bent pins, or poor connection in the dashboard harness
- Internal failure of the HVAC control module or associated front module
3. Symptoms You Will Notice
- Automatic climate control fails to maintain set temperature
- HVAC system may blow only hot or only cold air
4. Step-by-Step Diagnosis
Scan for additional codes and verify B1250 is present
Visually inspect the in-car temperature sensor and its connector for damage or corrosion
Check sensor resistance and compare to manufacturer specifications
Test wiring continuity and check for shorts between sensor and HVAC module
If wiring and sensor are good, suspect a faulty HVAC control module
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, the vehicle is safe to drive. The issue only affects automatic climate control; manual HVAC functions may still work.
How much does it cost to fix?▼
Repair costs typically range from $100 to $400, depending on whether the sensor, wiring, or control module needs replacement.