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B2A2111

In-Car Temperature Sensor signal circuit short to ground — Seal 6 EV

Thermal Management System

In-Car Temperature Sensor signal circuit short to ground.

This sensor typically mounts near the center instrument panel air vent or inside the HVAC duct and uses a Negative Temperature Coefficient (NTC) thermistor.

Normal operating voltage ranges from 0.5-4.5V (varying with temperature).

When the HVAC ECU detects the sensor signal line voltage remaining below 0.5V for longer than the set time threshold (typically 2-5 seconds), it determines a short to ground.

This fault causes the air conditioning system to lose the cabin ambient temperature feedback signal, resulting in automatic temperature control failure, disrupted compressor start-stop logic, and abnormal outlet air temperature (continuous maximum cooling or heating).

The fault may also affect the battery thermal management system comfort control strategy and, in severe cases, trigger Level 3 fault protection to limit air conditioning power.

The B2A2111 fault code on the Seal 6 EV indicates a short to ground in the in-car temperature sensor signal circuit. Severity is high because the HVAC system can lose cabin temperature feedback, causing automatic climate control faults, abnormal cooling or heating, and possible reduced air conditioning power. Common causes include damaged wiring insulation shorting to the body or moisture inside the sensor. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Seal 6 EV
  • 1Long-term vibration wears the sensor wiring harness insulation where it passes through the dashboard metal frame or firewall, shorting the signal wire to body ground.
  • 2Failure or moisture ingress of the internal thermistor package in the cabin temperature sensor causes an internal short circuit between terminals.
  • 3Poor drainage from the air conditioning evaporator housing causes water accumulation in the air duct. Water ingress and corrosion at the sensor connector short the pins to ground.
  • 4Missing wiring harness retaining clip after removing and refitting the centre control panel or dashboard during repair work, causing the wiring harness to contact a sharp-edged metal bracket.
  • 5After water ingress or flooding in the front compartment or passenger cabin, water residue on the sensor connector (usually located in the passenger-side air duct or inside the center console) causes a micro short circuit.
What To Do
  • 1
    Connect the BYD VDS diagnostic tool, read fault codes to confirm B2A2111 is a current active fault, record the voltage value in the freeze frame data (usually 0.0V or close to 0V), and check for accompanying historical faults such as B2A2013 (open circuit).
  • 2
    Remove the center control panel or passenger-side glove box. Locate the in-cabin temperature sensor (on Song/Qin series, usually behind the A/C control module or inside the center air vent duct). Visually inspect the connector for oxidation, water stains, or backed-out pins.
  • 3
    Disconnect the sensor connector. Use a multimeter to measure the resistance between the two terminals on the sensor body. Standard value at 25°C: 1.5-2.5kΩ. If the resistance is <100Ω, this indicates an internal sensor short circuit. Replace the sensor assembly.
  • 4
    If the sensor is normal, measure the resistance between the harness-side signal wire (usually yellow/green or white) and body ground. Normal resistance is >10MΩ. If continuity exists, trace the wiring route. Inspect the dashboard mounting bracket, firewall pass-through, and any contact points between the harness and metal edges.
  • 5
    Check the 32-pin or 40-pin air conditioning controller connector (located behind the central control head unit or inside the passenger-side dashboard). Confirm there are no backed-out pins or corrosion. Measure the 5V reference voltage output at the controller terminal to verify it is normal.
  • 6
    Repair the damaged wiring harness: If only the insulation is damaged, wrap the wire with waterproof tape and install corrugated conduit for protection. If copper strands are broken, solder the wires and seal the repair with heat-shrink tubing. Restore the wiring harness to its factory routing and securing points to prevent contact with sharp edges.
  • 7
    Reinstall all components, clear the fault code, start the vehicle, and set the air conditioning to AUTO mode. Monitor the data stream to verify the 'Interior Temperature' value updates with ambient temperature changes (the variation range must match the actual temperature). Run the system for 10 minutes to confirm the fault code does not return.
Real-World Cases
BYD DTC AI Analysis

2018 Song MAX: Air conditioning inoperative after dashboard removal and refitting

✓
Had a navigation system installed at an out-of-town aftermarket shop. The dashboard wasn't fully reassembled. While driving, the climate panel displayed "Please check A/C system" and VDS logged code B2A2111. Inspection found the installer had pinched the sensor wiring harness between the dashboard metal bracket and plastic trim. The insulation chafed through, causing the signal wire to short to ground. Repaired the damaged harness section, rerouted the wiring and fitted rubber grommets. Fault resolved.
BYD DTC AI Analysis

Qin EV300 abnormal temperature display after water wading

✓
After driving through approximately 30cm of water, the air conditioning auto mode failed and constantly blew hot air. The diagnostic tool showed active fault code B2A2111. Inspection found water beneath the cabin carpet. The cabin temperature sensor connector at the bottom of the centre dashboard air duct had water inside; electrolytic corrosion between the pins caused a short to ground. Drained the connector, cleaned it with precision electrical contact cleaner, and blow-dried it. Insulation resistance measured normal and the fault cleared. Also check the evaporator drain hose for blockages.
BYD DTC AI Analysis

Qin Pro DM sensor internal short due to aging

✓
Vehicle is four years old. Recently the AC cooling has been intermittent, with the dash occasionally displaying a thermal management fault. VDS detected B2A2111 intermittently. Removed the sensor and measured resistance: at room temperature it read only 50Ω and was unstable (normal is approximately 2kΩ), indicating the internal thermistor package had failed short. Replaced the genuine cabin temperature sensor (part number: EQ-8127000 or model-specific equivalent), cleared the fault code, and AC temperature control accuracy returned to normal.
BYD DTC AI Analysis

2019 Song MAX: Missing wiring harness retaining clips caused wear

✓
When driving on rough roads, the air conditioning system triggered intermittent warnings; no warnings appeared when stationary. Investigation revealed the sensor wiring harness retaining clip fractured where it passes through the passenger side dashboard frame. The harness moved within the aperture, causing the insulation to chafe against sharp metal edges and wear through, creating an intermittent short to ground. Repaired the damaged harness section and re-secured it with cable ties and foam tape to eliminate contact with metal components. Fault has not recurred.
Other Seal 6 EV Fault Codes
B1108For the BYD Song MAX (2017–2019), DTC B1108 indicates a short circuit in the PM2.5 air quality detection module (dust sensor) or its wiring harness. The sensor uses laser scattering to detect in-cabin and outside PM2.5 concentrations and transmits data to the HVAC ECU via the LIN bus or an analog signal. Short circuit conditions include: 1) Sensor power supply wire (+5V/+12V) shorted to ground 2) Signal wire shorted to power or ground 3) Short circuit in the sensor's internal photoelectric detection circuit This fault prevents the automatic climate control from switching between fresh air and recirculation based on air quality. The system enters fail-safe mode (typically forced recirculation). Severe short-circuit current can destroy the HVAC ECU sampling circuit. The system classifies this as a Level 3 severe fault and restricts vehicle operation to prevent electrical fires or controller damage. For other BYD models (such as the Qin EV, E5, and Song DM), B1108 indicates a driver-side sunload sensor fault, reflecting differences in DTC definitions across models.B110811This DTC indicates a short circuit in the air conditioning system PM2.5 air quality sensor (rapid detector). Specifically, abnormal continuity exists between the sensor power supply circuit or signal output circuit and body ground or battery positive. This causes the control module (ACU/air conditioning controller) to detect abnormal current or a voltage signal outside the valid range (typically 0V or supply voltage). The PM2.5 sensor monitors internal and external particulate concentrations, providing the data the automatic air conditioning system uses to switch between fresh air and recirculation modes. A short circuit disables the air quality monitoring function. This fault may force the air conditioning system into recirculation protection mode and trigger related thermal management system faults, as the air conditioning system acts as a key actuator in vehicle thermal management. In severe cases, the short circuit current can damage the internal sampling circuit of the air conditioning controller or overheat the wiring harness.B1109DTC B1109 indicates an open circuit in the communication line between the air conditioning system PM2.5 air quality sensor (dust concentration sensor) and the air conditioning control unit (AC ECU), or an open circuit within the sensor internal circuitry. Typically located in the air conditioning intake duct, this sensor monitors real-time PM2.5 particle concentration inside and outside the vehicle. It provides data to the automatic air conditioning system for intelligent switching between fresh air and recirculation modes and for controlling the air purification device. During an open circuit fault, the AC ECU cannot receive the air quality signal, triggering the system fail-safe mode. Symptoms typically include failure of the automatic recirculation function, abnormal air purification indicator light operation, or abnormal air quality data displayed on the air conditioning panel. Severe cases may compromise the cabin environment control strategy, but do not directly affect vehicle driving safety.B1737DTC B1737 indicates the Supplemental Restraint System (SRS) detected abnormal continuity between the right middle-row side airbag squib circuit (typically the second-row right seat side airbag or right curtain airbag) and the vehicle power supply (B+, battery positive). The SRS ECU monitors the airbag inflator resistance via an internal current source (normal resistance: 2.0–3.0 Ω). If the ECU detects the voltage across the inflator circuit remaining close to battery voltage (>5 V and approaching 12 V) instead of the expected low potential or floating state, it identifies a short to power. This fault prevents the airbag from deploying normally during a collision because the short circuit bypasses the firing current. In extreme cases, abnormal current can cause unintended deployment, posing a severe safety hazard.B173BDTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Common problems reported for Seal 6 EV →Seal 6 EV overview →
Data confidence: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.