AU
B132112

This fault code indicates a short to ground in the plate heat exchanger (PHE) outlet temperature sensor signal circuit, or an internal sensor short circuit — Seal U

Thermal Management System

This fault code indicates a short to ground in the plate heat exchanger (PHE) outlet temperature sensor signal circuit, or an internal sensor short circuit.

This sensor typically utilizes an NTC (negative temperature coefficient) thermistor to monitor the coolant or refrigerant temperature exiting the PHE, serving as a key feedback component for the thermal management system.

The short circuit sends an abnormal voltage signal (typically near 0V) to the ECU, causing the system to falsely detect an extreme temperature state.

This triggers the thermal management protection strategy, resulting in: forced electric compressor shutdown, battery cooling circuit interruption, restricted PTC heating function, or activation of the 'Power System Malfunction' reduced power mode.

Continued driving may overheat the battery pack or drive motor due to the lack of effective temperature monitoring, creating a thermal runaway risk.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Internal short circuit in the sensor body: Prolonged exposure to high temperatures and high humidity ages the NTC thermistor. Encapsulation failure causes an internal short circuit, and the resistance value approaches 0 Ω.
  • 2Physical damage to the wiring harness: The plate heat exchanger is in the high-temperature area of the front compartment. A loose harness retaining clip allows the harness to rub against sharp metal edges, damaging the insulation and shorting the signal wire (usually Pin 2) to body ground.
  • 3Connector short circuit due to water ingress: An aged front compartment low-voltage connector seal allows water to enter during wading or high-pressure washing, causing a pin-to-pin or pin-to-ground short circuit and often leaving signs of corrosion.
  • 4Assembly process defect: Improper wiring harness routing during repair allows sharp metal bracket edges to cut the harness, or an incompletely seated sensor connector causes the terminal to shift and contact the housing.
  • 5ECU sampling circuit fault (rare): A shorted internal pull-down resistor in the air conditioning controller or thermal management module continuously pulls the signal line low.
What To Do
  • 1
    Safety Preparation and Verification: Disconnect the high-voltage service disconnect and wait 5 minutes for the high-voltage capacitors to discharge. Use the VDS2000/BYD dedicated diagnostic tool to read the freeze frame data. Record the ambient temperature, vehicle speed, and temperature difference between the heat exchanger inlet and outlet at the time of the fault.
  • 2
    Initial visual inspection: Inspect the plate heat exchanger outlet temperature sensor connector (usually located on the battery cooler or Chiller outlet pipe) for looseness, backed-out pins, or water ingress. Inspect the wiring harness for secure mounting and wear at the firewall and battery pack edge.
  • 3
    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 resistance should be 1.5-2.5 kΩ (refer to the workshop manual for specific values). If the resistance is <100 Ω or infinite, replace the sensor.
  • 4
    Harness continuity and insulation test: Disconnect the corresponding connector from the air conditioning controller (or thermal management module). Measure the continuity resistance between the sensor connector signal terminal and the controller terminal (should be <1Ω). Measure the resistance between this terminal and body ground (should be >10MΩ; if <1kΩ, this confirms a short to ground).
  • 5
    Isolate the short circuit in sections: If the wiring harness shorts to ground, use the half-split method. Strip the harness sheath at the midpoint of the pathway and measure to systematically locate the damage. Inspect the bends routed along the front compartment side member and the edge of the battery pack housing.
  • 6
    Repair and Verification: Repair the damaged wiring harness (wrap with waterproof heat-shrink tubing, or replace the entire harness section if necessary), or replace the faulty sensor. Restore all connections and clear the DTC. Start the vehicle, turn on the A/C cooling/heating, and observe if the outlet temperature value in the data stream changes with operating conditions (the value should vary appropriately between -10°C and 80°C).
  • 7
    Road test verification: Perform a dynamic road test for at least 20 minutes. Monitor the data synchronization of all temperature sensors in the thermal management system. Confirm the fault code does not return and the system does not trigger abnormal protection.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin Pro EV: Internal short circuit in plate heat exchanger sensor caused air-con failure.

✓
Vehicle arrived with a 'cooling system fault' warning on the dashboard and no A/C cooling. Read DTCs: B132112 (plate heat exchanger outlet temperature sensor short) and U131587 (thermal management CAN communication fault). Measured resistance at the sensor connector: only 12Ω (normal 2kΩ), indicating the sensor's internal NTC element had shorted. Replaced the plate heat exchanger outlet temperature sensor (part no. XW-1E-XXX). After replacement, live data showed the outlet temperature recovering from an abnormal -40°C to 32°C. A/C operation returned to normal and the fault cleared.
BYD DTC AI AnalysisFrom Chinese market (translated)

Worn front compartment wiring harness causing intermittent short circuit on BYD Qin EV300

✓
Customer reported intermittent fault warnings and reduced power. DTC B132112 appeared intermittently. Inspection found the plate heat exchanger temperature sensor wiring harness chafing against a metal bracket at the left chassis rail in the engine bay. The insulation had worn through, exposing the copper conductors. On rough roads, the damaged wiring contacted the body earth, triggering a short circuit fault. Repair: Repaired damaged wiring (wrapped 3 layers, outer layer waterproof insulation tape), rerouted and secured harness, and fitted a rubber grommet to prevent recurrence. The fault has not returned.
BYD DTC AI AnalysisFrom Chinese market (translated)

Sensor connector shorted due to water ingress after wading

✓
After heavy rain and wading through water, the thermal management warning light came on. A diagnostic scan retrieved DTC B132112. Removed the plate heat exchanger outlet temperature sensor connector and found obvious water stains and copper corrosion inside. Analysis indicated the connector seal had deteriorated, allowing water to enter via capillary action along the wiring harness during wading. Cleaned the connector terminals with electronic cleaner and dried them with compressed air, applied conductive protective grease, replaced the waterproof seal, and the fault was resolved. Advised the customer to periodically inspect the sealing condition of low-voltage connectors in the front compartment.
BYD DTC AI AnalysisFrom Chinese market (translated)

False fault: Low ECU software version caused sampling anomalies

✓
Multiple 2018 Qin Pro DM vehicles reported fault code B132112, but actual measurements of the sensor and wiring harness were normal. Per the technical upgrade guidance, the AC controller software V1.2 on this batch had a bug where the ADC sampling threshold was set too tight, causing false short-circuit faults under electromagnetic interference. Solution: Upgrade the AC controller software to V1.5, which optimises the temperature sensor signal filtering algorithm. A one-month follow-up after the upgrade confirmed the fault did not recur.
BYD DTC AI AnalysisFrom Chinese market (translated)

Post-repair fault: Failure to bleed cooling system after coolant replacement caused false sensor reading.

✓
After replacing the battery coolant, the vehicle logged DTC B132112. Inspection found the technician had not followed the standard bleeding procedure, creating an air lock inside the plate heat exchanger and abnormal coolant flow. The outlet temperature fluctuated wildly (dropping suddenly from 60°C to -20°C), triggering the ECU's short-circuit protection (falsely diagnosing a circuit fault). Ran the thermal management system bleeding procedure again: used the vacuum filling equipment to evacuate the system for 30 minutes, tightened the bleed bolt to the specified torque of 6–8 N·m. The fault code cleared automatically and temperature data returned to normal.
Other Seal U 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.B110913DTC B110913 indicates an open signal circuit for the PM2.5 rapid detector (in-cabin air quality sensor). This sensor typically mounts inside the air conditioning system intake duct. It monitors in-cabin PM2.5 concentration in real time and provides data to the automatic air conditioning system for intelligent control of the air purification function. The BYD diagnostic protocol uses sub-code '13' to specifically indicate an open signal circuit. Although this fault theoretically affects a comfort feature, BYD Qin series vehicles classify it as a Level 3 (severe) fault. This classification occurs because the air conditioning system interacts with the battery thermal management system (e.g., monitoring battery cooling intake air quality). The fault can disable the automatic air conditioning mode and prevent the air purification function from operating. In extreme cases, it affects the battery compartment intake air quality assessment, triggering the 'repair immediately' strategy.B110AThis DTC indicates interrupted CAN bus communication or abnormal data between the air conditioning control unit (ACU) and the PM2.5 air quality sensor. The PM2.5 sensor monitors particulate concentration inside and outside the vehicle and provides the basis for purification control in the automatic air conditioning system. The ACU triggers this fault if it fails to receive a valid CAN message from the sensor within the specified period (usually 100-500 ms), if message verification fails, or if the signal frame times out. Although this fault does not affect vehicle driving safety, it disables the automatic air purification function. The air conditioning system cannot automatically switch between recirculation and fresh air modes or activate the air purification mode based on air quality. A persistent fault may restrict the thermal management strategy.
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]