As a seasoned automotive technician specializing in BYD EV models, I recently encountered a challenging case involving a BYD car that presented intermittent warnings on the dashboard, indicating “Assisted Driving Function Temporarily Unavailable.” This issue occurred in a 2025 BYD Yuan UP intelligent driving version equipped with a TZ200XSW motor. The vehicle had covered approximately 1,837 kilometers, and the fault would sporadically trigger during normal operation, causing the system to exit assisted driving mode. In this article, I will share my first-hand experience in diagnosing and resolving this problem, focusing on the ADAS (Advanced Driver-Assistance Systems) components, using detailed tables and formulas to summarize key aspects. Throughout this discussion, I will emphasize the importance of thorough inspection and calibration in maintaining the reliability of BYD EV systems.
Upon initial inspection, I connected the vehicle to a diagnostic tool, specifically the VDS system, to retrieve fault codes from the ADAS module. The codes indicated several issues: B1F9101, which pointed to a connection circuit fault in the front wide-angle right-side camera; B1FE300, suggesting an SN inconsistency in the right front-side camera; and B1FE700, indicating an SN inconsistency in the right surround-view camera. These fault codes are critical in BYD EV models, as they can disrupt the entire ADAS functionality, leading to safety concerns. To systematically analyze the problem, I considered multiple potential causes, including faults in the triple-camera assembly, issues with the ADAS domain controller, problems in the video signal transmission lines, or software and calibration errors in the ADAS system. The complexity of this BYD car’s ADAS network required a methodical approach, as any misalignment or hardware failure could cascade into broader system failures.
To begin the diagnostic process, I referred to the repair manual for BYD EV vehicles, which outlines procedures for handling SN inconsistency faults in cameras. The first step involved attempting to enter the calibration mode for the ADAS system. However, during this phase, the VDS tool repeatedly displayed a “Response Timeout” error, preventing access to the calibration program. This was a significant hurdle, as calibration is essential for synchronizing the multiple cameras in a BYD EV. I then proceeded to check the data stream from the ADAS domain controller, which showed that cameras 1 through 11 were operational, but their calibration results indicated they were uncalibrated or abnormal. This discrepancy highlighted the need for a deeper investigation into the hardware components.
Given the fault code related to the front wide-angle right-side camera connection circuit, I focused on inspecting the wiring harness. After removing the cover plate on the front windshield where the triple-camera assembly is housed, I discovered a fracture at the root of the connector for the front wide-angle right-side camera. This damage could interrupt the signal transmission, explaining the intermittent nature of the fault in this BYD car. I replaced the affected harness and conducted a road test, but the issue persisted, indicating that the problem might be more complex. Consulting the circuit diagram, I identified that the harness for this camera includes a coaxial cable running from the ADAS domain controller’s M6 connector to the camera itself. A thorough re-inspection confirmed no issues with pin dislodgment or looseness, so I moved on to electrical measurements.
Using a multimeter, I measured the voltage at the terminals of the camera harness, obtaining a reading of 13.08 V, which falls within the normal operating range for BYD EV systems. This result suggested that the power supply was adequate, pointing toward potential faults in either the ADAS domain controller or the triple-camera unit. To isolate the issue, I performed a swap test by replacing the triple-camera assembly with a known functional unit. After this intervention, the ADAS domain controller no longer generated the “front wide-angle right-side camera connection circuit fault” code. Subsequently, I installed a new triple-camera and proceeded with a multi-camera calibration, which was successful, ultimately resolving the fault. This case underscored that multiple fault points—such as the damaged harness and defective camera—can coexist, requiring comprehensive checks in BYD EV repairs.
The calibration process for ADAS systems in BYD EV models is highly dependent on specific environmental and operational conditions. To ensure accurate calibration, several requirements must be met, as summarized in the table below. These criteria are crucial for achieving reliable performance in BYD car ADAS functionalities, and they often involve complex interactions between sensors and external factors.
| Requirement Category | Specifications |
|---|---|
| Weather Conditions | Clear skies, no fog or haze, ensuring clear visibility of lane markings. |
| Lighting Conditions | No direct sunlight on the camera being calibrated. |
| Road Conditions | Straight, flat roads with minimal slope (longitudinal gradient < 1°), no cross-slopes; at least 1 km of straight road for maneuvers; urban settings with minimal congestion. |
| Driving Parameters | Speed maintained between 30–60 km/h; straight-line driving with minimal turns; smooth acceleration and deceleration (lateral acceleration ≤ ±0.2g, longitudinal acceleration within ±0.3g). |
| Lane Line Selection | Structured roads with rich static objects, clear textures, and lane lines; avoid pure white structures; prefer three-lane scenarios with consistent widths and dashed or solid lines for adjacent lanes. |
In addition to these practical steps, understanding the underlying electrical principles is vital for diagnosing BYD EV systems. For instance, Ohm’s law, expressed as $$V = I \times R$$, where V is voltage, I is current, and R is resistance, can be applied to verify circuit integrity in camera connections. In this case, the voltage measurement confirmed that the power delivery was within specs, but the fault persisted due to component-level issues. Furthermore, signal integrity in coaxial cables used in BYD car ADAS networks can be analyzed using the characteristic impedance formula for transmission lines: $$Z_0 = \sqrt{\frac{L}{C}}$$, where Z_0 is the characteristic impedance, L is inductance per unit length, and C is capacitance per unit length. For the coaxial cables in this BYD EV, the specified impedance was 50 Ω, and any deviation due to damage could lead to signal reflection and data loss, contributing to the observed faults.
Another critical aspect is the calibration algorithm itself, which often involves mathematical models to align camera perspectives. For example, in multi-camera systems of BYD EV models, the homography transformation can be represented as: $$H = K \cdot R \cdot K^{-1}$$, where H is the homography matrix, K is the camera intrinsic matrix, and R is the rotation matrix. This transformation ensures that images from different cameras are accurately mapped for ADAS functions. During the calibration of this BYD car, failures to enter the mode could stem from inconsistencies in these matrices due to hardware faults. The table below summarizes the fault codes and their implications, which I used to guide the diagnosis process.
| Fault Code | Description | Potential Causes |
|---|---|---|
| B1F9101 | Front Wide-Angle Right Camera Connection Circuit Fault | Damaged harness, faulty connector, or domain controller issue in BYD EV. |
| B1FE300 | Right Front-Side Camera SN Inconsistency | Mismatched serial number, calibration error, or camera failure in BYD car. |
| B1FE700 | Right Surround-View Camera SN Inconsistency | Similar to B1FE300, often related to software or hardware sync issues. |
Throughout this repair, I emphasized the importance of a systematic approach for BYD EV models, as the integration of multiple cameras and controllers requires precise coordination. For instance, the voltage measurement of 13.08 V was consistent with the expected range, but it alone wasn’t sufficient; the swap test revealed the camera’s role in the fault. This highlights that in BYD car diagnostics, combining electrical tests with physical inspections and component substitutions can efficiently isolate issues. Moreover, the calibration timeout error was likely a secondary effect of the primary hardware faults, as the ADAS domain controller could not communicate properly with the compromised camera.
To further elaborate on the technical details, the ADAS domain controller in BYD EV systems processes data from up to 11 cameras, and any inconsistency can trigger faults. The calibration process involves optimizing parameters such as focal length and distortion coefficients, which can be modeled using lens distortion formulas like: $$r = \sqrt{(x – x_c)^2 + (y – y_c)^2}$$ and $$\theta = \arctan\left(\frac{y – y_c}{x – x_c}\right)$$, where (x_c, y_c) is the optical center, and r and θ are radial and angular components used for correcting image distortions. In this BYD car, the inability to calibrate initially was due to the broken connector and faulty camera, which disrupted these calculations. After replacement, the calibration succeeded, allowing the BYD EV to restore full ADAS functionality.
In conclusion, this case demonstrates the intricacies of diagnosing and repairing ADAS issues in BYD EV models. The interplay between hardware faults, such as damaged harnesses and defective cameras, and software requirements, like precise calibration, necessitates a holistic approach. For technicians working on BYD car systems, it’s essential to follow structured protocols, utilize diagnostic tools effectively, and adhere to environmental conditions for calibration. By sharing this experience, I aim to highlight common pitfalls and best practices, ensuring that BYD EV owners receive reliable and safe driving assistance. Future advancements in BYD EV technology may incorporate more robust fault-detection algorithms, but for now, meticulous inspection remains key to resolving such complex issues.