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U014987

DTC U014987 indicates a communication link interruption between the battery thermal management controller (usually integrated into the Battery Management System (BMS) or a separate thermal management control unit) and the battery thermal circuit electric coolant pump — Atto 3

Thermal Management System

DTC U014987 indicates a communication link interruption between the battery thermal management controller (usually integrated into the Battery Management System (BMS) or a separate thermal management control unit) and the battery thermal circuit electric coolant pump.

This pump drives battery coolant circulation and typically uses LIN bus (CAN bus on some models) for digital communication.

The controller triggers this fault when it fails to receive pump status feedback signals (such as speed, temperature, or fault status) within a specified period (generally 100-200ms), or when it cannot send control commands (such as target speed requests).

This fault forces the battery thermal management system into open-loop control or degraded mode, limiting fast-charging power and power output.

Extreme cases may trigger battery high-temperature protection.

5
Cases Logged
Real-World Cases
BYD DTC AI Analysis

Poor contact in the front-end wiring harness of the Qin EV battery pack caused an intermittent communication fault.

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A 2019 Qin EV intermittently displayed "Check Power System" on the instrument cluster while driving, accompanied by DTC U014987. Technicians connected a VDS scan tool and reviewed live data; the battery thermal management pump status showed "communication timeout" when the fault occurred. They inspected the low-voltage harness connector at the front of the battery pack where it mates to the body harness and found an intermittent loose connection at the LIN bus terminal, with resistance fluctuating between 0.5 and 50 Ω. Disassembling the connector revealed a fractured internal locking clip that caused the terminal to back out. Solution: Replaced the battery pack low-voltage harness assembly, re-crimped the terminals and applied conductive paste. Technicians ran the thermal management system self-test with VDS and confirmed the fault cleared.
Original source ↗
BYD DTC AI Analysis

Loose ground point on Qin EV thermal management water pump caused communication loss

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A Qin EV lit the powertrain warning light while driving on rough roads. Scanning showed DTC U014987 (Lost communication with battery thermal management electric water pump). The fault returned when the vehicle bounced. Diagnosis found a loose bolt at ground point G107 (on the left front frame rail), causing intermittent power loss to the water pump control module. The water pump connector also had a loose communication line. Fix: Tightened ground point G107 to 8–10 N·m, repaired the LIN wiring inside the water pump connector, cleared the codes, and completed a 20 km road test with no recurrence.
Original source ↗
BYD DTC AI Analysis

e5 water pump power fuse holder burned, causing communication fault

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A BYD e5 (same thermal management platform as the Qin EV) could not fast charge. The dashboard displayed a thermal management fault, and the BMS stored DTC U014987. The LV battery management data stream showed abnormal thermal management water pump status. Inspection found burn damage on the 15A water pump fuse holder inside the front compartment distribution box. This caused pump supply voltage to fluctuate between 8-12V, below the LIN bus minimum operating voltage of 9V. Replaced the front compartment distribution box assembly, repaired the fuse holder contact surface, and confirmed stable 12V at the pump. Cleared the fault codes; fast charging returned to normal.
Original source ↗
BYD DTC AI Analysis

Burnt thermal management relay contacts caused water pump communication failure on Qin EV

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Qin EV displayed "Thermal Management System Fault" (DTC U014987) during cold start after sitting overnight. The fault appeared consistently at startup but cleared once warm. Multimeter measurement of the water pump supply voltage showed a drop below 6V during startup. Further inspection found burnt contacts on the thermal management water pump relay inside the front compartment fuse box. High inrush current during startup pulled the voltage down, resetting the water pump control module. Replaced the front compartment fuse box assembly, checked water pump operating current (normal: <8A), confirmed no abnormalities, and delivered the vehicle.
Original source ↗
BYD DTC AI Analysis

Seal 06 thermal management controller software defect caused water pump communication error

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A Seal 06 DM-i (thermal management architecture similar to the Qin EV) intermittently displayed thermal management warnings on the dashboard with reduced A/C cooling. Scanning showed fault code U014987 and related communication errors. The LIN bus termination resistance measured 45Ω (standard: 60Ω), causing signal reflection. Oscilloscope testing revealed waveform distortion. The battery thermal management controller had outdated software with a known protocol compatibility issue. Solution: Upgraded the thermal management controller to the latest software and added a 120Ω resistor in parallel at the LIN network end to match impedance. Cleared the fault codes and monitored for one week with no recurrence.
Original source ↗
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: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.