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B2AB997

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

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 Qin Plus indicates the electric air-conditioning compressor is working above its safe load limit. This is a medium-severity fault that may reduce cooling or shut the compressor down to protect the high-voltage system. Common causes include internal compressor wear or seizure, low lubrication, high A/C pressure, a clogged condenser, or refrigerant overcharge. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Electric compressor internal mechanical seizure or lubrication failure: scroll plate wear, bearing seizure, degraded or insufficient refrigerant oil, causing increased mechanical resistance torque.
  • 2Abnormal A/C system pressure: High condensing pressure (dirty or clogged condenser, faulty cooling fan, high ambient temperature), low evaporating pressure (faulty expansion valve, blocked refrigerant line), or refrigerant overcharge (excess liquid refrigerant poses a liquid slugging risk).
  • 3High-voltage power supply system fault: 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 circulation causing compressor overheating.
  • 5Control strategy or sensor fault: compressor phase current sensor drift, CAN bus communication fault causing VCU to miscalculate 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 verify B2AB997 is a current fault. Read the data stream and check the 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 the high-voltage connectors (B23/B24) for burn marks or backed-out pins. Measure the contact resistance (should be <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). Verify if the high-side pressure is excessively high or the low-side pressure is excessively low.
  • 4
    Compressor mechanical inspection: Disconnect the high and low-pressure lines and check the compressor turning resistance (manually turn the clutch plate; it must rotate smoothly without binding, resistance torque <3 N·m). Check the refrigerant oil condition (colour, impurities, quantity). If necessary, use dedicated equipment to test the compressor insulation (>20 MΩ) and coil resistance (three-phase balanced, deviation <10%).
  • 5
    Thermal management cooling system inspection: Clean the condenser surface (use a dedicated cleaning agent; avoid damaging the cooling fins), check the electric fan low- and high-speed operation (low speed approx. 1000 rpm, high speed approx. 2000 rpm), and check the coolant level and circulation (electronic water pump operation).
  • 6
    Control module and wiring check: 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 wiring short or open circuits.
  • 7
    Repair verification: After repairing or replacing the faulty part, draw a vacuum (-0.1 MPa, hold for 30 minutes), charge the refrigerant as specified (R134a, usually 550-650 g), and perform the compressor run-in procedure (gradually increase speed). Observe 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 return.
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 Qin Plus 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.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.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.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 Qin Plus →Qin Plus 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.