What Does B1253 Mean?
DTC B1253 indicates that the Body Control Module (BCM) or Climate Control Module has detected an abnormally low voltage in the internal air temperature sensor circuit, consistent with a short to ground condition. This sensor monitors cabin air temperature for automatic climate control systems. The module identified that the signal voltage dropped below the expected minimum threshold, triggering this fault code.
Common Causes
45%
Damaged or chafed wiring harness causing short to ground between sensor and control module
30%
Failed internal air temperature sensor with internal short circuit
15%
Corrosion or moisture intrusion in sensor connector causing ground path
10%
Faulty climate control module or BCM with internal circuit failure
Diagnostic Steps
1
Step 1: Locate the internal air temperature sensor (typically mounted in or near the dash/HVAC housing) and visually inspect the sensor, connector, and wiring for obvious damage, chafing, pinched wires, corrosion, or moisture intrusion
2
Step 2: Disconnect the internal air temperature sensor connector and measure resistance across the sensor terminals using a digital multimeter; typical thermistor sensors show 2,000-10,000 ohms at room temperature (verify manufacturer specs), while a shorted sensor will show near 0 ohms
3
Step 3: With sensor disconnected, check for continuity between each sensor circuit wire and vehicle ground; any continuity (less than 5 ohms) indicates a short to ground in the wiring harness
4
Step 4: Inspect the wiring harness routing from sensor to control module, paying special attention to areas where wires pass through firewalls, near sharp metal edges, or through hinged areas where chafing occurs
5
Step 5: If wiring and sensor test normal, measure voltage on the sensor signal wire at the sensor connector with ignition on; should see reference voltage (typically 5V or 12V depending on system); 0V indicates control module issue
6
Step 6: Clear codes, reconnect all components, operate climate control system through various modes, and verify code does not return; monitor live sensor data to confirm proper temperature readings
Estimated Repair Cost
$120 - $450
Parts + labor, varies by vehicle and location
DTC B1253 indicates that the Body Control Module (BCM) or Climate Control Module has detected an abnormally low voltage in the internal air temperature sensor circuit, consistent with a short to ground condition. This sensor monitors cabin air temperature for automatic climate control systems. The m...
The most common cause of B1253 (Air Temperature Internal Sensor Circuit Short To Ground) is: Damaged or chafed wiring harness causing short to ground between sensor and control module
Typical repair costs for B1253 range from $120 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This fault does not affect vehicle safety or drivability and it is safe to continue driving. Climate control automatic temperature regulation may not function properly, requiring manual adjustment of HVAC settings, but heating and cooling functions remain operational.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1253 to identify the root cause.
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Quick Info
Category
Body
System
Climate Control System (HVAC)
Difficulty
Type
Manufacturer
Recommended Tools
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