AU
B122013

This DTC indicates an open circuit in the thermal management system right heatsink temperature sensor (NTC thermistor) — Atto 3

Thermal Management System

This DTC indicates an open circuit in the thermal management system right heatsink temperature sensor (NTC thermistor).

In BYD Qin EV/DM models, this sensor typically mounts on the PTC heater heatsink or the motor controller (MCU) IGBT heatsink to monitor power device operating temperatures in real time.

When sensor wiring breaks, the sensor fails, or the connector makes poor contact, the control module detects a voltage signal outside the valid range (typically because the 5V reference voltage fails to complete a circuit) and logs this fault.

Because the system cannot accurately monitor the heatsink temperature, it triggers a thermal management protection strategy.

This strategy may disable the PTC heater or limit motor power output.

In extreme cases, power devices may overheat and fail, making this a severe fault.

4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Temperature sensor aging or physical damage: Internal thermistor element is open circuit. Resistance measures infinite at room temperature (normally around 10kΩ, varying with temperature).
  • 2Wiring harness worn or broken: High temperatures in the motor or front compartment degrade the sensor wiring harness insulation, or vehicle vibration causes the harness to rub against sharp edges, breaking the copper wires.
  • 3Poor connector contact: Loose sensor plug, backed-out terminal, oxidized or corroded pins, or incomplete connector seating during servicing causing an intermittent connection.
  • 4Water ingress corrosion: Water enters the sensor connector during front compartment washing or wading, causing terminal oxidation or a short circuit that burns out the terminals and results in an open circuit.
  • 5Control module sampling circuit fault (rare): Damage to the internal sampling resistor or reference voltage circuit in the air conditioning controller or thermal management module causes a false sensor open circuit detection.
What To Do
  • 1
    Diagnostic tool data stream analysis: Connect the VDS or a dedicated diagnostic tool and read the 'right-side heat sink temperature' data stream. If the reading shows -40℃, 255℃, or a fixed value, confirm an abnormal signal. Simultaneously read the relevant PTC or MCU temperature data to determine if the fault involves the same component.
  • 2
    Sensor body inspection: Disconnect the sensor connector and use a multimeter to measure the resistance between the two sensor terminals. At room temperature (25°C), the standard value is approximately 10 kΩ ±5%. If the resistance is infinite or deviates significantly from the temperature-resistance curve, replace the sensor.
  • 3
    Circuit continuity check: Leave the sensor disconnected and measure harness continuity from the control module end. Check the harness resistance between the corresponding pin on the BMS or A/C controller and the sensor connector; resistance must be less than 1Ω. Test for a short to ground and a short to power to confirm only an open circuit exists, not a short circuit.
  • 4
    Connector inspection: Visually inspect the sensor plug and socket terminals for oxidation, burn marks, backed-out pins, or looseness. Test the terminal retention force using a dedicated probe. Clean the plug/socket with electrical contact cleaner or replace as necessary.
  • 5
    Repair verification: After repairing or replacing the faulty component, clear the fault code. Start the vehicle and run the PTC heater or drive motor to increase the heat sink temperature. Observe the data stream to verify the temperature value changes accordingly, and confirm the fault is resolved.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin EV300 PTC heater temperature sensor open circuit due to aging.

✓
A 2017 BYD Qin EV300 with 120,000 km on the clock displayed ‘Power System Fault’ on the instrument cluster and had no heating. Read DTC B122013. Live data showed right-side heat sink temperature at –40°C. Removed and inspected the PTC heater water outlet temperature sensor (right-side heat sink sensor); the connector was oxidised and the sensor measured infinite resistance. Replaced the sensor. The new sensor measured 10.2 kΩ at 22°C ambient. Reconnected the connector, live data returned to normal, and heating function restored.
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin Pro DM: Front compartment wiring harness wear caused an intermittent open circuit.

✓
2018 Qin Pro DM. Intermittent DTC B122013 with no cabin heating when the fault occurred. Inspection found the fault only appeared over bumps. Traced the wiring harness from the PTC controller to the sensor and found it had worn through at the firewall clip from prolonged vibration, leaving only a few copper strands connected; the circuit broke completely on rough roads. Repaired the harness by cutting out the damaged section, soldering in an extension, and protecting it with high-temperature tape and corrugated conduit. Adjusted the routing to avoid contact with sharp edges. Fault resolved.
BYD DTC AI AnalysisFrom Chinese market (translated)

Sensor connector corroded from water ingress after wading.

✓
A 2019 Qin Pro DM lit the cooling system warning light the day after wading through deep floodwater. Pulling codes gave B122013. Inside the right-side radiator temperature sensor connector, I found water stains, green copper corrosion, and infinite resistance across the terminals. Water had wicked up the harness by capillary action during the water crossing, oxidizing the contacts and causing an open circuit. I replaced the sensor connector (with pigtail), dried the original harness and treated it with corrosion protection, applied conductive grease, and reconnected. Fault cleared.
BYD DTC AI AnalysisFrom Chinese market (translated)

Connector not reseated after repair caused false fault code

✓
After front collision repairs, the vehicle logged DTC B122013. Inspection found that after replacing the front compartment wiring harness, the technician had swapped the right-side radiator temperature sensor connector with a nearby two-pin connector (front compartment temperature sensor). They plugged in, but the mismatched pin configuration caused an open circuit. Correcting the connections cleared the fault code and restored normal operation. During repairs, pay attention to the error-proof design of similar connectors to prevent mix-ups.
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
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. Sources: [1]