As a researcher in the field of automotive engineering, I have dedicated significant effort to understanding the intricacies of new energy vehicles, particularly the BYD EV series. The 2019 BYD Qin EV represents a pivotal model in the evolution of electric vehicles, and its fault diagnosis processes are critical for maintenance professionals. In this paper, I will elaborate on common fault scenarios, including failure to power up the low-voltage system, inability to power up the high-voltage system, and charging abnormalities, all based on my extensive experience with BYD car systems. The diagnostic approach I propose involves a systematic流程: initial observation of fault phenomena, in-depth analysis using circuit diagrams, and precise confirmation through targeted检测 steps. This methodology has been validated through multiple case studies, demonstrating its effectiveness in real-world applications for BYD EV models. The growing adoption of BYD car technologies underscores the importance of reliable diagnostic protocols, and this work aims to contribute to the advancement of the new energy vehicle maintenance industry.
The BYD EV platform incorporates complex electrical systems that require meticulous attention to detail during troubleshooting. My research focuses on the 2019 BYD Qin EV, a model known for its efficiency but occasionally prone to specific faults. By emphasizing the use of quantitative measurements and circuit analysis, I have developed a robust framework for diagnosing issues in BYD car systems. This paper will explore various fault types, supported by tables and mathematical formulas to summarize key points. For instance, voltage and resistance measurements are fundamental in identifying abnormalities, and I will use equations like $V = I R$ to explain underlying principles. Throughout this discussion, I will frequently reference BYD EV and BYD car to highlight the relevance of these concepts to this specific vehicle series. The integration of such diagnostic methods can enhance the reliability and safety of BYD EV operations, ultimately supporting the broader goals of sustainable transportation.
Common Typical Faults in BYD EV
In my work with the 2019 BYD Qin EV, I have encountered several recurring faults that can impede vehicle performance. These issues often stem from the intricate interplay between low-voltage and high-voltage systems in BYD car designs. Below, I detail the most prevalent faults, organized into categories for clarity. Each fault is analyzed with a focus on observable phenomena, potential causes, and step-by-step检测 procedures. I employ tables to summarize phenomena and causes, while mathematical formulas are used to quantify normal and abnormal values during measurements. This structured approach ensures that technicians can efficiently address problems in BYD EV models, reducing downtime and improving service quality.
Failure to Power Up Low-Voltage System
The low-voltage system in BYD EV is essential for basic functions like unlocking doors and initiating the start-up sequence. Faults here can prevent the vehicle from operating entirely. Based on my observations, two common sub-faults are particularly relevant for BYD car systems: smart key module ground point disconnection and brake light switch self-damage. Each of these has distinct characteristics that I will explore in depth.
Smart Key Module Ground Point Disconnection
In BYD EV models, the smart key module is a critical component for keyless entry and start-up. When the ground point becomes disconnected, it leads to a cascade of issues. I have compiled the typical phenomena into a table for easy reference.
| Phenomenon Number | Description |
|---|---|
| 1 | Remote control fails to unlock the vehicle normally. |
| 2 | Keyless entry does not function; pressing the micro-switch causes the key indicator to flash, but the door remains locked. |
| 3 | Inner door lock operates correctly, but the vehicle cannot power up the low-voltage system. |
The root causes in BYD car systems often include module malfunction, wiring issues, or key mismatches. To diagnose this, I follow a precise检测流程 that involves voltage and resistance measurements. For example, with the ignition in ON position, I measure the voltage between points KJG01/15-KG25(A)/1 and KG25(A)/9/10-node SP2718. The normal voltage should be $V_{\text{normal}} = 12\,V$, but in faulty BYD EV cases, I often find $V_{\text{measured}} = 0.3\,V$. This discrepancy indicates an abnormality, as per Ohm’s law where $V = I R$; a drop in voltage suggests increased resistance or an open circuit. Subsequently, after powering down and disconnecting the battery, I measure the resistance between node SP2718 and ground point E06. The expected resistance is $R < 1\,\Omega$, but a measurement of $R = \infty$ confirms a disconnection. This fault directly impacts the BYD car’s ability to initiate the low-voltage system, highlighting the importance of secure ground connections in BYD EV designs.
Brake Light Switch Self-Damage
Another frequent issue in BYD EV models involves the brake light switch, which is vital for enabling the start-up sequence. When damaged, it manifests through specific symptoms that I have summarized in the following table.
| Phenomenon Number | Description |
|---|---|
| 1 | Pressing the brake pedal does not cause the key indicator to flash. |
| 2 | During start-up, the instrument panel displays a prompt to press the brake踏板 and start button, but the OK light fails to illuminate. |
| 3 | The instrument panel remains unlit, and the vehicle cannot power up the low-voltage system. |
Potential causes in BYD car systems include switch failure, wiring faults, BCM issues, or related circuit problems. My detection approach involves voltage checks under different conditions. For instance, I measure the voltage between G2I/21 and G28/1, where the normal value is $V_{\text{normal}} = 12\,V$. In operational BYD EV units, this measurement aligns, but when the brake踏板 is pressed, the voltage should drop due to the circuit activation. However, in faulty cases, I observe $V_{\text{measured}} = 11.78\,V$ with no change, indicating an issue. After power down, I measure the resistance between G28/1 and G28/2; the normally closed contacts should show $R = \infty$ when the brake is applied, but I often find $R = 0.3\,\Omega$, suggesting the contacts are stuck closed. This fault underscores the sensitivity of BYD car electrical systems to component wear and tear, necessitating regular inspections for BYD EV owners.
Failure to Power Up High-Voltage System
The high-voltage system in BYD EV is responsible for powering the drivetrain and other critical components. Faults here can render the vehicle immobile. From my experience, issues like BMS CAN-H to ground short circuits and pre-charge/positive contactor power shorts are common in BYD car models. I will dissect each with detailed analysis and mathematical formulations.
BMS CAN-H to Ground Short Circuit
In BYD EV, the Battery Management System (BMS) CAN bus facilitates communication between modules. A short circuit to ground can disrupt this, leading to high-voltage power-up failures. The phenomena associated with this fault are tabulated below.
| Phenomenon Number | Description |
|---|---|
| 1 | With ignition ON, the P light and OK light on the instrument panel do not illuminate, and battery level is not displayed. |
| 2 | The instrument panel shows messages like “Check vehicle network” and “Check power system,” accompanied by a beeping sound. |
| 3 | The vehicle cannot power up the high-voltage system. |
Causes may involve faults in the power CAN, gateway, or related wiring in BYD car systems. My detection流程 includes resistance and voltage waveform measurements. First, I power down and disconnect the battery, then measure the resistance between BK45B/16-G19/9 and BK45B/17-G19/10. The normal resistance is $R = 65\,\Omega$, and in functional BYD EV units, this holds true. Next, with ignition ON, I check the waveform voltage between BK45B/16-G19/9 and BK45B/2/3-node SP2080; the expected voltage is $V_{\text{normal}} \approx 2.5\,V$, but in faulty cases, I measure $V_{\text{measured}} = 0.6\,V$. This can be modeled using the formula for voltage division in a short circuit: $V_{\text{measured}} = V_{\text{source}} \frac{R_{\text{short}}}{R_{\text{total}}}$, where $R_{\text{short}}$ is the resistance at the fault point. Further, after unplugging the BMS B connector, I measure the resistance between BK45B/9/14 and BK45B/2/3-node SP2080; it should be $R = \infty$, but I often find $R = 20.5\,\Omega$, indicating a virtual short. This fault highlights the complexity of CAN networks in BYD EV and the need for precise measurements in BYD car diagnostics.
Pre-charge/Positive Contactor Power Short to Ground
This fault in BYD EV affects the contactors that manage high-voltage power distribution. When a short occurs, it prevents the system from energizing properly. The typical phenomena are summarized in the table below.
| Phenomenon Number | Description |
|---|---|
| 1 | With ignition ON, the P light and OK light illuminate, and battery level displays normally. |
| 2 | The instrument panel indicates “Check power system,” and the cooling fan runs continuously. |
| 3 | The vehicle cannot power up the high-voltage system. |
Root causes in BYD car systems include BMS faults, wiring issues, or problems with the充配电总成. My detection steps focus on voltage consistency and resistance checks. For example, with ignition ON, I measure the voltage upstream and downstream of F1/34. The upstream voltage is $V_{\text{upstream}} = 12\,V$, but downstream, I find $V_{\text{downstream}} = 0.5\,V$ instead of the expected $12\,V$. The resistance of F1/34 should be $R < 1\,\Omega$, but it measures $R = \infty$, indicating an open fuse. After power down, I check for shorts to ground downstream of F1/34 and find a direct short. Then, with the BMS A connector unplugged, I measure the resistance between BK45(A)/7-node SP2073 and BK45(A)/2-node SP3601; it should be $R = \infty$, but I get $R = 0.3\,\Omega$, confirming a short circuit. This fault demonstrates the critical role of contactors in BYD EV high-voltage systems and the importance of insulation integrity in BYD car designs.
Inability to Charge Normally
Charging issues are a common concern for BYD EV owners, often stemming from signal line faults. In the 2019 BYD Qin EV, problems with the CC (Charging Control) line can prevent normal charging. I have documented the phenomena and detection methods based on my hands-on experience with BYD car charging systems.
| Phenomenon Number | Description |
|---|---|
| 1 | With ignition ON, the P light and OK light illuminate, battery level displays, but inserting the charging gun does not light up the charging indicator red plug. |
| 2 | The vehicle cannot charge normally. |
Causes may include CC line faults, CP line issues, or charging gun malfunctions in BYD car systems. My detection流程 involves voltage and resistance measurements at specific points. With ignition ON, I measure the voltage between BK46/4 and BK53(B)/2; the normal value is $V_{\text{normal}} = 12\,V$, and in working BYD EV units, this is confirmed. However, after inserting the charging gun, the voltage should drop due to circuit engagement, but in faulty cases, it remains at $12\,V$. This can be expressed as $\Delta V = 0$, where $\Delta V$ is the expected voltage change. After power down and disconnecting the battery, I unplug the BK53 B connector and measure the resistance between BK46/4 and BK53(B)/2; it should be $R = \infty$, but I often find $R = 1\,k\Omega$. This virtual resistance indicates a poor connection, disrupting the charging process in BYD EV. The formula for power loss due to resistance, $P = I^2 R$, explains why even a small resistance can cause significant issues in BYD car charging efficiency.
General Diagnostic Framework for BYD EV
Based on my extensive work with BYD EV models, I have developed a generalized diagnostic framework that can be applied to various faults in BYD car systems. This framework integrates observation, analysis, and confirmation phases, supported by mathematical models to quantify findings. For instance, I often use the concept of fault probability $P_f$ based on historical data from BYD EV cases, where $P_f = \frac{N_f}{N_t}$, with $N_f$ being the number of fault occurrences and $N_t$ the total observations. Additionally, I employ tables to compare normal and abnormal parameters across different BYD EV components.
| Parameter Type | Normal Value | Abnormal Value | Fault Implication |
|---|---|---|---|
| Voltage (Low-V) | $12\,V$ | $<11\,V$ or $>13\,V$ | Indicates power supply issues in BYD car systems |
| Resistance (Ground) | $<1\,\Omega$ | $R = \infty$ or $R > 100\,\Omega$ | Suggests open circuits or poor connections in BYD EV |
| CAN Voltage | $2.5\,V$ (approx.) | $<1\,V$ or $>4\,V$ | Points to communication faults in BYD car networks |
Furthermore, I incorporate formulas like $V_{\text{drop}} = I \times R_{\text{fault}}$ to calculate voltage drops in faulty BYD EV circuits, where $R_{\text{fault}}$ is the resistance at the fault point. This mathematical approach enhances the precision of diagnoses for BYD car technicians, enabling them to identify issues quickly. My framework also emphasizes the importance of iterative testing; for example, if initial measurements in a BYD EV do not match expectations, I recompute values using $V_{\text{corrected}} = V_{\text{measured}} \pm \Delta V_{\text{error}}$, where $\Delta V_{\text{error}}$ accounts for instrument inaccuracies. This systematic method has proven effective in reducing diagnostic time for BYD EV models, contributing to higher customer satisfaction and reliability in the BYD car ecosystem.
Conclusion
In this paper, I have detailed the fault diagnosis and troubleshooting methodologies for the 2019 BYD Qin EV, drawing from my firsthand experiences and analyses. By focusing on common issues such as low-voltage and high-voltage power-up failures, as well as charging abnormalities, I have demonstrated the value of a structured approach that combines observation, circuit analysis, and precise measurements. The use of tables and mathematical formulas, including equations like $R = \frac{V}{I}$ for resistance calculations, has enabled a quantitative understanding of faults in BYD EV systems. This diagnostic流程 is not only feasible but also essential for the ongoing professional development of the new energy vehicle maintenance sector, particularly as BYD car technologies continue to evolve. I encourage further research into automated tools that can leverage these principles for BYD EV models, potentially integrating machine learning algorithms to predict faults based on historical data. Ultimately, this work underscores the importance of rigorous diagnostics in ensuring the longevity and performance of BYD EV vehicles, supporting the broader adoption of sustainable transportation solutions.