What Does B1252 Mean?
This code indicates the Body Control Module (BCM) or climate control module has detected a short-to-voltage condition in the internal cabin air temperature sensor circuit. The sensor's signal wire is reading battery voltage instead of the expected reference voltage, suggesting the circuit is shorted to a power source. This affects the vehicle's automatic climate control system's ability to accurately monitor and regulate cabin temperature.
Common Causes
45%
Damaged or chafed wiring harness causing sensor signal wire to contact a power wire or powered component
30%
Failed internal air temperature sensor with internal short circuit to power pin
15%
Corroded or damaged sensor connector terminals allowing cross-contamination between power and signal circuits
10%
Failed climate control module with internal short circuit on sensor input channel
Diagnostic Steps
1
Step 1: Locate the internal air temperature sensor (typically behind dashboard near HVAC unit or within climate control head unit) and visually inspect wiring harness for visible damage, chafing, melting, or contact with hot/powered components
2
Step 2: Disconnect the internal air temperature sensor connector and use a digital multimeter to measure voltage on the signal wire at the harness side connector with ignition ON - should read 5V reference voltage, not battery voltage (12-14V)
3
Step 3: With sensor disconnected, measure resistance of the sensor between signal and ground terminals - typical values range 2-5k ohms at room temperature; reading near zero ohms indicates internal short
4
Step 4: If harness shows battery voltage with sensor disconnected, inspect entire harness routing from sensor to climate control module for pinched wires, check for aftermarket accessory installations that may have damaged wiring, and verify no corrosion or bent pins in connectors causing shorts
5
Step 5: If wiring and sensor test good, test climate control module input by back-probing the module connector at the sensor signal pin with key ON - should read 5V reference; battery voltage here indicates module failure
6
Step 6: After repairs, clear codes, cycle ignition, operate climate control system through all modes and temperature settings, and verify code does not return and cabin temperature reading is accurate
Estimated Repair Cost
$100 - $450
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) or climate control module has detected a short-to-voltage condition in the internal cabin air temperature sensor circuit. The sensor's signal wire is reading battery voltage instead of the expected reference voltage, suggesting the circuit is shorted...
The most common cause of B1252 (Air Temperature Internal Sensor Circuit Short To Battery) is: Damaged or chafed wiring harness causing sensor signal wire to contact a power wire or powered component
Typical repair costs for B1252 range from $100 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to continue driving as this only affects automatic climate control accuracy. The HVAC system may default to manual mode or predetermined settings, but heating and cooling functions remain operational. Non-urgent repair unless cabin comfort is severely compromised.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1252 to identify the root cause.
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Quick Info
Category
Body
System
Climate Control System
Difficulty
Type
Manufacturer
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