AU
B2AB997

DTC B2AB997 indicates the electric air-conditioning compressor (E-Compressor) operating load exceeds the system-calibrated safety threshold — Seal 6 EV

Thermal Management System

DTC B2AB997 indicates the electric air-conditioning compressor (E-Compressor) operating load exceeds the system-calibrated safety threshold.

The compressor controller or vehicle control unit (VCU) triggers this fault in the BYD Qin EV thermal management system when it detects a compressor drive current continuously exceeding the rated value (typically >15-20A, depending on operating conditions), an abnormal drop in speed feedback (stall risk), or an abnormal rise in torque demand.

The system then registers an 'excessive load'.

This protective fault prevents compressor mechanical damage, high-voltage circuit overload, or thermal management system failure.

The fault can reduce air-conditioning cooling capacity and automatically shut down the compressor.

Extreme cases may trigger high-voltage interlock protection, affecting battery thermal management functions.

The B2AB997 fault code on the Seal 6 EV indicates the electric air-conditioning compressor is working harder than the safe calibrated limit. Severity is medium, as cooling may be reduced and the compressor may shut down to prevent damage. Common causes include internal compressor wear or binding, and abnormal A/C pressure from a blocked condenser, fan fault, or refrigerant issue. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
5
Cases Logged
5
Causes
Likely Causes — Seal 6 EV
  • 1Internal mechanical binding or lubrication failure in the electric compressor: scroll plate wear, bearing seizure, or degraded or insufficient refrigerant oil, causing increased mechanical resistance torque.
  • 2Abnormal A/C system pressure: high condenser pressure (dirty or blocked condenser, cooling fan failure, high ambient temperature), low evaporator pressure (expansion valve failure, blocked line), or excessive refrigerant charge (excess liquid refrigerant causes liquid slugging risk)
  • 3High-voltage power supply system malfunction: unstable traction battery voltage (undervoltage or overvoltage), poor contact in the high-voltage wiring harness (burnt or loose connectors causing increased resistance), compressor controller (IPM) power module fault
  • 4Poor heat dissipation in the thermal management system: severely contaminated front-end module (condenser + radiator), abnormal electric fan speed (PWM signal fault or motor aging), or restricted coolant flow causing compressor overheating.
  • 5Control strategy or sensor fault: compressor phase current sensor drift, CAN bus communication fault causing the VCU to misjudge the load, or incorrect software calibration parameters.
What To Do
  • 1
    Fault Confirmation and Data Reading: Use the VDS2000/VDS3000 diagnostic tool to read all fault codes and confirm if B2AB997 is a current fault. Read the data stream, focusing on compressor current (A), speed (rpm), duty cycle (%), high-voltage bus voltage (V), A/C high-side pressure (MPa), and condenser outlet temperature (°C).
  • 2
    High-voltage safety check: Perform the high-voltage power-down procedure. Wear insulated gloves. Measure the insulation resistance of the compressor high-voltage wiring harness (standard value ≥20MΩ). Inspect high-voltage connectors (B23/B24) for burn damage or backed-out pins. Measure the contact resistance (<0.1Ω).
  • 3
    A/C system pressure check: Connect the manifold gauge set. Check the static pressure (approximately 1.0-1.2 MPa at 25°C). Check the dynamic high-side pressure (1.5-2.5 MPa, depending on ambient temperature) and low-side pressure (0.15-0.25 MPa) to verify if the high-side pressure is excessively high or the low-side pressure is excessively low.
  • 4
    Compressor mechanical inspection: Disconnect high-pressure and low-pressure lines. Check compressor turning resistance (manually turn the clutch plate; it must rotate smoothly without binding, resistance torque <3N·m). Check refrigerant oil condition (colour, impurities, quantity). If necessary, use dedicated equipment to test compressor insulation (>20MΩ) and coil resistance (three-phase balance, deviation <10%).
  • 5
    Thermal management cooling system inspection: Clean the condenser surface (use a dedicated cleaning agent to avoid damaging the cooling fins); check the electric fan low-speed and high-speed operation (low speed approx. 1000rpm, high speed approx. 2000rpm); check the coolant level and circulation (electric water pump operation).
  • 6
    Control module and wiring inspection: Measure the compressor controller low-voltage power supply (12V±0.5V) and ground (<0.1Ω). Check the CAN-H and CAN-L voltages (2.5V±0.5V) and waveforms (dominant level: CAN-H 3.5V / CAN-L 1.5V) to rule out short or open circuits in the wiring.
  • 7
    Repair verification: After repairing or replacing the faulty component, draw a vacuum (hold at -0.1 MPa for 30 minutes) and charge the refrigerant as specified (R134a, usually 550-650 g). Perform the compressor run-in procedure (gradually increase speed). Monitor the data stream during a road test to confirm the current stabilizes within the normal range (5-12 A) and the fault code does not recur.
Real-World Cases
BYD DTC AI Analysis

Qin EV 2019: Worn compressor scroll plate causing excessive load

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Vehicle: 2019 BYD Qin EV, 85,000 km. Symptoms: Approximately 5 minutes after turning on the AC, the vents blew warm air and the thermal management warning light illuminated. Retrieved DTC B2AB997. Diagnosis: Live data showed compressor current spiking to 25 A (normal ≤15 A) before the system shut down. Static pressures read normal, but dismantling the compressor revealed severe wear to the scroll plates, with internal metal debris causing mechanical seizure. Repair: Replaced the electric compressor assembly. Flushed the AC lines, condenser and evaporator with dedicated cleaner, and replaced the desiccant. Recharged the system with refrigerant and compressor oil (SP-A2 oil, 150 ml) to specification. Fault resolved.
BYD DTC AI Analysis

Severely clogged condenser caused excessive high-side pressure

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Vehicle: Qin EV 2019, 60,000 km, used year-round on construction sites. Symptoms: AC kept shutting down in hot summer weather. Scanner logged DTC B2AB997. Diagnosis: Data stream showed 38°C ambient with condenser outlet at 85°C (normal <65°C). High-side pressure read 3.2 MPa (normal 2.0–2.5 MPa) and compressor current stayed above 18 A. Found the condenser completely clogged externally with mud and willow fluff. The cooling fan ran at high speed but couldn't dissipate heat properly. Fix: Thoroughly cleaned the condenser fins (used a fin comb to straighten deformed fins), replaced the cabin filter, and cleaned the gap between the radiator and condenser. Cleared the codes; system returned to normal.
BYD DTC AI Analysis

Poor contact in high-voltage wiring harness caused abnormal load.

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Vehicle: BYD Qin EV 2019, accident-repaired vehicle. Symptom: Intermittent AC cooling failure, intermittent DTC B2AB997. Diagnosis: Data stream showed high voltage bus voltage dropping instantly from 420V to 380V when the compressor engaged, with large current fluctuations. Inspection found burn marks inside high voltage harness connector B23 (front compartment high voltage distribution box to compressor). Contact resistance measured 2.3Ω (normal <0.05Ω), causing insufficient input voltage to the compressor controller. The controller increased current to maintain power, triggering overload protection. Repair: Replaced high voltage harness assembly, cleaned contacts and applied conductive paste, tightened connector. Fault resolved.
BYD DTC AI Analysis

Refrigerant overcharge causing liquid slugging risk

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Vehicle: Qin EV 2019. Fault appeared after a workshop topped up the refrigerant. Symptoms: Compressor noise when the AC turned on, followed by DTC B2AB997 and shutdown. Diagnosis: Recovery yielded 850g of refrigerant (standard: 600g). High-side pressure hit 2.8MPa at 25°C ambient. Compressor drew 16A. Liquid refrigerant entered the compressor before fully evaporating, causing liquid slugging and high mechanical load. Solution: Recovered all refrigerant and recharged to the standard 600g±25g. Replaced the receiver drier (liquid may have entered). Compressor load returned to normal.
BYD DTC AI Analysis

Compressor controller IPM module fault

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Vehicle: Qin EV 2019, 42,000 km. Symptoms: AC not cooling at all. Throwing B2AB997 and B2AB809 (compressor drive fault). Diagnosis: Measured compressor three-phase winding resistance balanced at 0.8 Ω; insulation normal. Controller low-voltage supply and signals normal. Internal IPM (Intelligent Power Module) in the controller failed, distorting the output current waveform and causing the phase current sensor to detect abnormally high current. Repair: Replaced compressor controller (some variants require the complete compressor assembly depending on configuration). Flashed control program to V2.3.1. Fault resolved.
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.