OBD-II trouble code
B1250: Air Temperature Internal Sensor Circuit Failure
The climate control module detected a fault in the in-cabin (interior) air temperature sensor circuit. The automatic climate control may not regulate temperature correctly, but the vehicle drives normally.
Quick facts
- System
- Body
- Category
- Body / HVAC Climate Control
- Severity
- Low severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $20 – $300
- DIY difficulty
- Intermediate DIY
What does B1250 mean?
B1250 is a manufacturer-specific body (B) code — used by Ford and others — defined as 'Air Temperature Internal Sensor Circuit Failure.' The in-car (internal) air temperature sensor measures the temperature inside the cabin and reports it to the automatic climate control module. The module uses that reading, along with outside-air and sunload data, to decide how much heating or cooling to deliver and to hold the temperature you set. Many of these sensors sit behind a small vent in the dash and use a tiny aspirator fan to draw cabin air across the sensing element.
The module sets B1250 when the sensor's circuit reads out of range — an open circuit, a short, or resistance that doesn't correspond to any plausible temperature. When that happens, the automatic climate control loses a key input and can no longer regulate cabin temperature accurately; it may blow air that is too hot or too cold, cycle oddly, or default to a fixed setting. Because it is a manufacturer-specific code, confirm the exact definition and sensor location against your make's service data.
This is a comfort/convenience fault, not a driveability or safety fault: the engine and everything else run normally. Importantly, a working sensor is frequently and unnecessarily replaced when the real problem is a damaged wire, a corroded connector, or a blown fuse in the circuit — so the wiring should be checked before the sensor is condemned.
Common causes
- Damaged, pinched, or broken wiring in the internal air temperature sensor circuit
- Corroded, loose, or disconnected connector at the sensor
- Blown fuse feeding the circuit
- Failed in-cabin air temperature sensor
- Clogged or failed sensor aspirator fan (on systems that use one)
- Fault in the climate control (HVAC) module itself
Symptoms
- Automatic climate control regulates temperature poorly or not at all
- Air blows too hot or too cold for the selected setting
- Climate control may default to a fixed output or manual-only operation
- Warning or error indication on the climate/information display in some vehicles
- No effect on engine or driving performance
Diagnostic steps
- 1.Scan the body/HVAC module and record B1250 and any companion climate-control codes.
- 2.Locate the in-cabin air temperature sensor for the specific make (often behind a dash vent, sometimes with an aspirator fan).
- 3.Inspect the sensor connector and wiring for corrosion, looseness, chafing, or breaks — the most common and cheapest cause.
- 4.Check the fuse feeding the circuit.
- 5.Measure the sensor's resistance and compare it to the specification at a known temperature to confirm whether the sensor itself is faulty.
- 6.If equipped, verify the aspirator fan runs and draws air across the sensor.
- 7.Repair the wiring/connector or replace the sensor as indicated, then clear B1250 and confirm the climate control regulates correctly.
Repair cost
$20 – $300
The in-cabin air temperature sensor is an inexpensive part, often $15-$60, and a wiring or connector repair can cost little to nothing as a DIY fix. Most of the cost is labor and diagnosis if the sensor is buried behind the dash. Because good sensors are frequently replaced unnecessarily, confirm the wiring and fuse before buying the part.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with cabin air temperature sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.