AU
U016487

ISO 15031 defines fault code U0164 as 'Lost Communication With HVAC (Air Conditioning Control Module)' — Atto 8

Thermal Management System

ISO 15031 defines fault code U0164 as 'Lost Communication With HVAC (Air Conditioning Control Module)'.

Sub-code 87 is a BYD-specific identifier indicating the BCC (Battery Cooling Controller/Body Control Computer) failed to receive key CAN messages from the air conditioning controller within a 500ms monitoring cycle: ID 0x1DB (ambient temperature, soft shutdown request) or 0x3CF (cabin compressor speed request, A/C request status).

This fault indicates a communication interruption between the HVAC sub-network (HVAC-CAN) and the Powertrain CAN or BMS network.

This interruption prevents the thermal management system from coordinating the electric compressor, PTC heater, and battery cooling circuit.

The system may trigger thermal management derating protection (power limitation or A/C disabled), but typically does not cause immediate vehicle immobilization.

The U016487 fault code on the Atto 8 indicates lost communication with the air conditioning control module, affecting HVAC and battery thermal management. Severity is medium; the car may limit power or disable A/C but usually remains drivable. Common causes include a blown fuse or poor HVAC module power/ground connection, or damaged CAN wiring. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
5
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Abnormal HVAC controller power supply: Causes include a blown F1/15 fuse in the dashboard fuse box, burnt terminals, backed out pins or poor connections at the IGN ignition signal wire, or a loose ground wire, causing intermittent power loss to the module.
  • 2CAN bus physical layer fault: Short or open circuit in the A/C sub-network CAN-H and CAN-L lines, terminating resistor deviation (normally approx. 60Ω), or wiring harness chafing and insulation damage at instrument panel frame bends.
  • 3HVAC module hardware fault: internal PCB water ingress and corrosion (often due to a blocked A/C drain hose causing condensate backflow), damaged CPU or CAN transceiver chip, software version mismatch (protocol conflict after OTA update)
  • 4Gateway communication interference: Gateway module fault between the powertrain and comfort networks causes cross-network message forwarding failure.
  • 5Wiring harness connector issue: Backed-out terminals, oxidation, corrosion, or excessive contact resistance (>5 Ω) at the B09 (white 20-pin) or B10 connector.
What To Do
  • 1
    Use the VDS2000/3000 diagnostic tool to read all DTCs. Check for accompanying DTC U0140 (Lost Communication with BCM) or B12C2 (Compressor Controller Fault). Read the data stream to confirm the HVAC module online status and communication voltage.
  • 2
    Check HVAC controller power supply: Measure voltage across fuse F1/15 in the fuse box (should be 12V±0.5V), check IGN signal wire voltage stability over bumps (should be >11V), and measure ground resistance (should be <1Ω).
  • 3
    Check the CAN bus: Disconnect the HVAC connector. Measure the voltage to ground at OBD pin 6 (CAN-H, 2.5-2.7V) and pin 14 (CAN-L, 2.3-2.5V). Measure the terminating resistance (after power-off, resistance at the HVAC connector should be 120Ω; total vehicle parallel resistance should be approximately 60Ω).
  • 4
    Physical connection check: Remove and inspect the HVAC module connector behind the glove box. Check if B09 pin 5 (IGN) has backed out, inspect the wiring harness for chafing against the metal dashboard frame, and check the connector for water stains or green oxidation.
  • 5
    Software diagnosis: Compare the HVAC module software version against the latest technical bulletin. Check if the head unit OTA update caused a protocol mismatch. If necessary, use VDS to perform 'Air Conditioning Controller Programming' and 'Air Flap Self-Learning'.
  • 6
    Drainage system inspection: Check the A/C drain hose for blockages (common during poplar fluff season), inspect the evaporator housing seal, and check the HVAC module mounting location for signs of water accumulation.
  • 7
    Component replacement and calibration: If diagnostics confirm module hardware damage, replace the HVAC controller (part number HA-8121100), perform 'Air Conditioning System Configuration' to write the vehicle VIN code, and perform 'Compressor Run-in' and 'Temperature Flap Calibration'.
Real-World Cases
BYD DTC AI Analysis

Song Pro DM climate control panel black screen; IGN signal pin backed out

✓
Symptoms: Air conditioning suddenly stopped working while driving. Multimedia display showed black screen or 'communication fault' on climate interface. VDS retrieved DTC U016487. Other functions normal. Diagnosis: CAN voltage at OBD port measured normal. Removed and inspected HVAC module inside centre console. Found pin 5 (IGN signal) of B09 connector (white, 20-pin) had backed out. Voltage dropped below 3 V over bumps, causing module to drop offline. Resolution: Re-crimped terminal and applied conductive adhesive. Secured wiring harness with cable ties to prevent chafing against dashboard frame. Cleared fault codes. Communication restored.
Original source ↗
BYD DTC AI Analysis

e5 450 ride-share: Burnt fuse holder with poor contact

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Symptoms: AC fails randomly, restores after restarting the vehicle, more frequent in hot weather. B12C2 fault code present. When the fault occurs, blower speed stays fixed but cannot be adjusted. Diagnosis: Live data showed the HVAC module dropping offline intermittently. Inspected the dashboard fuse box and found the F1/15 fuse pin burnt; measured contact resistance at 8.5Ω (abnormal). Discovered an aftermarket dash cam power tap had deformed the fuse box base. Repair: Replaced the dashboard fuse box assembly. Removed the aftermarket power feed wiring. Disconnected the battery negative terminal for 5 minutes to reset the HVAC module. Recalibrated the air door positions.
Original source ↗
BYD DTC AI Analysis

Qin Plus EV module damaged by water ingress after OTA update

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Symptoms: After the head unit OTA update, the AC system logged DTC U016487 and the code wouldn't clear. The system kept blowing hot air, the AC switch flashed, and the display showed "System Initialization Failed". Diagnosis: The HVAC software V1.02 didn't match the head unit V2.15 protocol. The module didn't respond to programming attempts. Removed the module and found visible water damage on the PCB from backflow due to a blocked AC drain pipe. Resolution: Replaced the AC control module (HA-8121100), cleared the drain pipe, and ran VDS to execute "AC System Configuration", "Air Door Self-Learning", and "Compressor Break-in" procedures.
Original source ↗
BYD DTC AI Analysis

Qin Pro EV air conditioning subnet CAN bus lines chafed and shorted

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Symptoms: A/C won't turn on after rain or car washes. Cluster shows "Thermal Management System Fault". Codes: U016487 and multiple U01** series communication faults. Diagnosis: Checked HVAC connector: CAN-H shorted to ground (0V). Traced harness and found the HVAC subnet backbone inside the dash chafed through at the steering column mounting bracket. Rainwater caused the short. Resolution: Repaired harness (rewrapped with waterproof tape), rerouted and added securing clips, replaced corroded HVAC connector.
BYD DTC AI Analysis

Qin EV300 ambient temperature data abnormality causes communication timeout

✓
Symptoms: No HVAC heat after winter morning starts. DTC U016487 set (1DB message loss). Fault cleared when ambient temperature rose at midday. Diagnosis: Factory scan tool showed HVAC module online but 1DB message counter not incrementing. External temperature sensor wiring checked OK. Found dry solder joint on HVAC internal temperature sampling circuit; poor contact at low temperatures caused message transmission timeout. Repair: Replace HVAC control module, or return to factory for PCB repair (resolder temperature sampling circuit).
Other Atto 8 Fault Codes
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.B110A02DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle). The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus. The fault is essentially a communication link layer timeout. Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage. Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function. In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 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.