B1855

Code

Other B — Body

Climate Control Air Temperature Internal Sensor Motor Circuit Short To Battery

Brand: Other

Type: B — Body

Views: UK: 16 EN: 35 RU: 19

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Damaged wiring contacting battery positive (chafing, pinched harness)
Corroded or pushed-back connector terminal making B+ contact
Failed/shorted air temperature sensor or blend/stepper motor (internal short to B+)
Faulty climate control / HVAC control module or driver transistor
Water intrusion in connector or module causing shorting
Improper aftermarket accessory wiring tied into HVAC circuits

Symptoms

HVAC temperature control incorrect or stuck
Blend door or temperature actuator not moving or operating erratically
Climate control fault message or reduced HVAC functionality
Possible stored HVAC-related DTCs and loss of closed-loop temperature control

What to check

Read and record all stored HVAC-related codes and freeze-frame data
Perform visual inspection of HVAC wiring harnesses and connectors for damage, pin corrosion, water intrusion, or aftermarket taps
Disconnect the air temperature sensor/actuator connector and check whether the code clears or changes
Backprobe the suspect harness pin(s) with ignition ON to check for battery voltage at rest and with HVAC commands
Measure resistance/continuity between the suspect circuit and battery positive (B+) with ignition OFF
Inspect related fuses and relays for evidence of damage

Signal parameters

Expected: sensor/actuator signal circuit should NOT show constant battery voltage when module is commanding off (voltage varies with command; consult vehicle-specific data)
If shorted: the suspect circuit will measure ~12V relative to chassis ground with ignition ON
With ignition OFF, resistance between circuit and B+ should be very high (open); a low resistance (
Actuator coil resistance (vehicle-specific) normally measures low ohms; an almost 0 Ω reading or direct short to B+ indicates internal shorting (refer to factory spec)

Diagnostic algorithm

Record codes and relevant freeze-frame. Do not replace parts without verifying wiring.
Visually inspect HVAC harness and connectors from the climate control module to the air temperature sensor/actuator for damage, water, or aftermarket splices. Repair obvious damage.
With ignition ON, backprobe the sensor/actuator connector pin. If it measures close to battery voltage (~12V) when it should not, suspect a short to B+.
Turn ignition OFF and measure resistance between the suspect circuit and battery positive. Low resistance indicates a short.
Disconnect the sensor/actuator. If the code clears or behavior changes, isolate between connector and module to locate the short.
Wiggle-test harness and connectors while monitoring voltage/resistance to find intermittent shorts.
If wiring and connectors check good, bench-test or swap the air temperature sensor/actuator (if available) to verify an internal short. Replace the faulty sensor/motor if confirmed.
If component replacement does not resolve the short, inspect or replace the climate control/HVAC module or repair the module driver circuit per manufacturer procedures.
After repairs, clear codes and perform HVAC exercise/test to confirm proper operation and that the DTC does not return.

Likely causes

Shorted internal wiring in the air temperature sensor or actuator motor
Wiring insulation damaged and contacting a 12V source
Corroded/filled connector causing conductive path to B+
Failed control module driver pin stuck at battery potential

Fault status

⚠️ Status

Climate Control Air Temperature Internal Sensor Motor Circuit Short To Battery (B1855) — sensor/actuator circuit detecting unintended battery positive connection.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours