What Does B1855 Mean?
This code indicates the climate control module has detected a short to battery voltage in the internal air temperature sensor motor circuit. The internal temperature sensor motor controls a blend door or sensor positioning mechanism that measures cabin air temperature. The control module detected voltage higher than expected on the control circuit, indicating the circuit is shorted to a power source rather than being properly controlled.
Common Causes
40%
Damaged or chafed wiring harness causing short to power in the sensor motor circuit
35%
Failed internal air temperature sensor motor with internal short circuit
15%
Corroded or damaged connector terminals at sensor motor allowing cross-circuit voltage
10%
Failed climate control module with shorted output driver circuit
Diagnostic Steps
1
Step 1: Perform visual inspection of the internal air temperature sensor motor and its wiring harness located typically behind the dashboard near the HVAC unit. Look for chafed wires, damaged insulation, melted connectors, or signs of water intrusion.
2
Step 2: Disconnect the internal air temperature sensor motor connector and use a digital multimeter to measure resistance between each motor terminal and battery positive. Should read open circuit (OL); any continuity indicates a short to power in the wiring harness.
3
Step 3: With connector still disconnected, measure resistance across the sensor motor terminals. Compare to manufacturer specifications (typically 50-500 ohms). Infinite resistance or very low resistance (under 10 ohms) indicates motor failure.
4
Step 4: Inspect the climate control module connector and measure voltage on the motor control circuit with ignition on and climate control activated. Should see pulsed voltage or controlled output, not constant battery voltage. Constant 12V indicates module failure.
5
Step 5: Repair or replace identified faulty component (wiring harness, sensor motor, or control module). Clear codes and cycle the climate control system through all temperature settings while monitoring live data to verify proper motor control and no return of the fault code.
Estimated Repair Cost
$150 - $650
Parts + labor, varies by vehicle and location
This code indicates the climate control module has detected a short to battery voltage in the internal air temperature sensor motor circuit. The internal temperature sensor motor controls a blend door or sensor positioning mechanism that measures cabin air temperature. The control module detected vo...
The most common cause of B1855 (Climate Control Air Temperature Internal Sensor Motor Circuit Short To Battery) is: Damaged or chafed wiring harness causing short to power in the sensor motor circuit
Typical repair costs for B1855 range from $150 to $650, 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. The climate control system may not accurately regulate cabin temperature, but all other vehicle systems remain functional. Repair can be scheduled at convenience.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1855 to identify the root cause.
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Quick Info
Category
Body
System
Climate Control System
Difficulty
Type
Manufacturer
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