What Does B1250 Mean?
This code indicates that the Body Control Module (BCM) or climate control module has detected a malfunction in the internal air temperature sensor circuit used by the HVAC system. This sensor measures cabin temperature to help the automatic climate control system maintain the desired temperature setting. The control module has identified a voltage reading outside the expected range, an open circuit, short circuit, or sensor failure.
Common Causes
45%
Failed internal air temperature sensor or aspirator fan motor
30%
Wiring harness damage, corrosion, or connector issues between sensor and control module
15%
Blocked or restricted air flow to the internal temperature sensor
10%
Failed Body Control Module or climate control module
Diagnostic Steps
1
Step 1: Locate the internal air temperature sensor (typically in the dashboard near the radio or center console with a small grille). Visually inspect the sensor grille for blockage from debris, coins, or objects that could restrict airflow to the sensor.
2
Step 2: Access the sensor connector and inspect for corrosion, bent pins, or moisture. Using a multimeter, backprobe the sensor connector and measure resistance across the sensor terminals with ignition off (typical range 2-5k ohms at 70°F, varies by manufacturer). Compare to specifications.
3
Step 3: With the connector still attached and ignition on, measure voltage supply from the control module (typically 5V reference). Check ground circuit for continuity to chassis ground (should be less than 1 ohm resistance).
4
Step 4: If sensor reads within specifications, check the aspirator fan motor operation by listening for airflow when HVAC system is activated. The aspirator draws cabin air across the sensor; if inoperative, the sensor cannot read accurately.
5
Step 5: If all wiring and sensor test good, perform a voltage wiggle test by gently moving the wiring harness while monitoring live data to identify intermittent connections.
6
Step 6: Clear the code, cycle the HVAC system through all modes, and verify the code does not return. Monitor internal temperature sensor readings in live data to confirm they track with actual cabin temperature changes.
Estimated Repair Cost
$150 - $450
Parts + labor, varies by vehicle and location
This code indicates that the Body Control Module (BCM) or climate control module has detected a malfunction in the internal air temperature sensor circuit used by the HVAC system. This sensor measures cabin temperature to help the automatic climate control system maintain the desired temperature set...
The most common cause of B1250 (Air Temperature Internal Sensor Circuit Failure) is: Failed internal air temperature sensor or aspirator fan motor
Typical repair costs for B1250 range from $150 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This code does not affect vehicle safety or drivability and it is safe to continue driving. The only impact is reduced automatic climate control functionality, as the system may not properly regulate cabin temperature or may default to manual mode.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1250 to identify the root cause.
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Quick Info
Category
Body
System
HVAC Climate Control System
Difficulty
Type
Manufacturer
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