AU
B1667

System definitions for DTC B1667 vary across BYD models — Atto 8

Safety System

System definitions for DTC B1667 vary across BYD models.

Original documentation classifies it under the SRS as "left side impact sensor short to ground." However, in practice for BYD F3, G6, S6, S7, Song, Tang, and Qin series models, B1667 generally indicates a Body Control System fault: "driver side (left) door mirror vertical adjustment motor fault/stuck." Based on circuit operation, the BCM (Body Control Module) identifies the fault by monitoring the drive current and position feedback signal of the door mirror vertical adjustment motor.

The BCM stores this DTC when it detects a short to ground, abnormal current (too high or too low), motor stall, or an open circuit in the motor circuit.

This fault disables the electric vertical adjustment of the door mirror.

It typically does not affect horizontal adjustment, mirror heating, or folding functions (if equipped).

5
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Worn carbon brushes, oxidized commutator, or internal short circuit in the rearview mirror vertical adjustment motor, resulting in abnormal drive current.
  • 2Rearview mirror drive mechanism (plastic worm gear, gear set) lacks lubrication, shows wear or breakage, or binds due to foreign matter (such as dust or rust particles).
  • 3Long-term bending of the door wiring harness at the A-pillar or hinge damages the insulation, causing a power wire short to ground or a signal wire open circuit.
  • 4Oxidized or burned internal contacts in the door mirror adjustment switch cause abnormal control signals or incorrect position feedback to the BCM.
  • 5Poor door mirror assembly sealing allows water intrusion from rain or car washing, causing internal motor moisture, corrosion, and a short circuit on the circuit board.
What To Do
  • 1
    Use a BYD dedicated diagnostic tool or generic OBD device to read the Body Control Module (BCM) fault codes. Confirm B1667 is present and check for an accompanying B1668 (right side) or other related fault codes.
  • 2
    Check the rearview mirror/window system fuse in the engine compartment or dashboard fuse box (commonly F16/15A or F17/20A). If blown, do not install a higher-capacity fuse. Locate the short circuit first.
  • 3
    Remove the driver-side door trim panel, disconnect the door mirror wiring harness connector, and measure the vertical adjustment motor winding resistance using a multimeter. The normal value is 2-5 Ω. A resistance of 0 Ω indicates an internal short circuit. An infinite reading indicates an open circuit or worn carbon brushes.
  • 4
    Turn the ignition switch to the ON position. Measure the voltage between the power supply terminal of the rearview mirror wiring harness connector and body ground. The reading should be the 12V battery voltage. Simultaneously check the ground wiring harness for continuity and contact resistance.
  • 5
    If circuit measurements are normal, remove and disassemble the door mirror assembly. Check the internal plastic gear set and worm drive mechanism for wear, breakage, or foreign objects. Clean and lubricate the moving parts using WD-40 or special grease.
  • 6
    Inspect the wiring harness at the door hinge and inside the rubber boot. Check for worn outer insulation or exposed copper strands shorting to the body metal. If damaged, repair the wire. Wrap the repair with multiple layers of heat-shrink tubing and insulating tape. Adjust the harness routing to prevent further chafing.
  • 7
    Replace the faulty component based on the inspection results (replacing the adjustment motor alone costs approximately RMB 180–300; replacing the door mirror assembly costs RMB 800–1200). After reassembly, clear the fault code, perform the up/down adjustment test, and confirm the fault code does not reappear.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD S7 side mirror internal gear set seized

✓
Vehicle: 2016 BYD S7, 80,000 km. Symptoms: Driver's side mirror will not adjust up or down electrically; left/right adjustment operates normally; no warning lights on the instrument cluster. Diagnosis: Scanned the BCM and retrieved DTC B1667 (driver's side mirror vertical motor jammed). Measured motor resistance at 3.2Ω (normal) and determined mechanical seizure. Dismantled the mirror assembly and found the internal gear set had seized due to long-term lack of lubrication. Solution: Replaced the driver's side mirror assembly; resolved the fault. Repair cost: Parts 850 yuan + Labour 150 yuan.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Song DM side mirror worm gear fractured

✓
Model: BYD Song DM. Symptom: Left side mirror vertical (up/down) electric adjustment inoperative. Slight clicking sound when operating the switch, but the mirror glass does not move. Diagnosis: DTC B1667. Checked fuse F16 – normal. Measured motor power supply at 12V – normal. Manual movement of the mirror showed significant binding. Disassembled the mirror housing and found the internal plastic worm gear broken and worn. Resolution: Replaced the mirror adjustment motor only (no need to replace the complete assembly). Part cost: ¥180. Labour: ¥100.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Tang DM wing mirror worm gear grease dried out

✓
Model: 2018 Tang DM. Symptom: Left side mirror vertical adjustment inoperative. Diagnosis: The dealer scanned code B1667 and quoted 1,200 yuan to replace the mirror assembly. An independent workshop disassembled the unit and found the worm drive mechanism seized due to dried grease and dust accumulation. Solution: Thoroughly cleaned the worm gear set, reapplied high-temperature grease, and reassembled. Mirror functions normally. Cost: Labour 50 yuan.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin Pro wing mirror wiring harness chafed and shorted at hinge

✓
Model: Qin Pro. Symptoms: Driver side mirror electric vertical adjustment and heating function both inoperative. Diagnosis: Read DTC B1667. Checked the shared fuse F16 (15A) for rear window demister and mirror heating and found it blown. Replaced it, but it blew again immediately. Found a short circuit. Close inspection found the mirror wiring harness insulation worn at the door hinge, copper wire shorting to the body. Solution: Repaired the damaged harness, re-wrapped it with insulation tape and corrugated tubing, and rerouted the harness. Cost: Parts 20 yuan + Labour 80 yuan.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Water ingress caused gear corrosion in the BYD G6 side mirror.

✓
**Model:** 2013 G6 1.5TI, 120,000 km. **Symptoms:** Driver's side mirror electric up/down adjustment inoperative; left/right adjustment works normally. **Diagnosis:** Connected Launch X431, retrieved DTC B1667. Measured power supply: normal. Applied power directly to the motor – it ran weakly with abnormal noise. Removed the mirror assembly and disassembled it. Found the internal gear set severely worn, with rust and debris (suspected previous water ingress). **Resolution:** Cleaned the gear set, applied grease, temporarily restored function. Recommended replacing the motor (estimated RMB 200–300). Owner opted to keep using it and monitor.
Original source ↗
Other Atto 8 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]