In my experience as an automotive technician specializing in BYD EV models, I frequently encounter complex issues related to the power system in these advanced hybrid vehicles. BYD car technologies, particularly in models like the Han DM-i, integrate sophisticated electronic control systems that require precise diagnostics. One common problem involves intermittent dashboard warnings such as “Check Power System,” which can lead to sudden power loss. This article details a real-world case where I diagnosed and resolved such an issue in a BYD EV, emphasizing the critical role of redundant sensor systems and thorough electrical testing. Throughout this discussion, I will highlight key aspects of BYD EV design and BYD car functionalities, using tables and formulas to summarize technical data and principles.
The vehicle in question was a BYD Han DM-i, equipped with a BYD472QB engine and the BYD E-CVT-2 hybrid system. The owner reported that during HEV mode operation, the dashboard occasionally displayed the “Check Power System” warning, accompanied by a loss of propulsion and inability to accelerate. In some instances, restarting the BYD car temporarily restored normal function, but the issue persisted intermittently. This behavior is typical in BYD EV models when there are faults in the electronic throttle system, which relies on redundant signals for safety.
Upon initial inspection, I connected a diagnostic tool to scan the vehicle’s systems. The scan revealed several fault codes stored in the vehicle control unit, specifically related to throttle signal anomalies. Below is a table summarizing these fault codes and their descriptions, which guided the subsequent diagnostics:
| Fault Code | Description |
|---|---|
| P001D65 | Throttle Signal Fault – Signal 2 Fault |
| P001D66 | Throttle Signal Fault – Validation Fault |
| P1D6500 | Throttle Signal Fault – Signal 2 Fault |
| P1D6600 | Throttle Signal Fault – Validation Fault |
These codes indicated potential issues with the accelerator pedal sensor signals, which are crucial for the BYD EV’s power management. Next, I proceeded to analyze the data stream from the vehicle control unit. The data showed the throttle position sensor readings under different conditions. When the accelerator pedal was not pressed, the throttle depth was 0%, and when fully pressed, it reached 95%. This data appeared normal at first glance, but the fault codes suggested underlying signal inconsistencies. The following table captures the data stream observations:
| Condition | Throttle Depth (%) |
|---|---|
| Pedal Not Pressed | 0 |
| Pedal Fully Pressed | 95 |
To delve deeper, I referred to the维修手册 and circuit diagrams for the BYD car. The fault scope included the vehicle control unit, accelerator pedal assembly, and related wiring harnesses. I inspected connectors such as BG44 (accelerator pedal), A02A (power domain), and BJA02 (engine compartment), checking for signs of moisture, corrosion, or pin dislodgment. No visible issues were found initially. Subsequently, I performed voltage measurements on key pins to assess signal integrity. Using a multimeter, I measured the voltages at pins BJA02-21 (throttle signal 2) and BJA02-18 (throttle signal 1) with the pedal not pressed. The results are summarized in the table below:
| Pin | Signal Type | Voltage (V) |
|---|---|---|
| BJA02-21 | Throttle Signal 2 | 0.35 |
| BJA02-18 | Throttle Signal 1 | 0.69 |
These voltages seemed within an acceptable range for a BYD EV under idle conditions, but the fault codes pointed to validation errors. Upon further physical inspection and manipulation of the wiring harness, I discovered that the terminal at pin BJA02-21 was not properly crimped during manufacturing, causing it to dislodge easily. This loose connection explained the intermittent signal faults, as the throttle signal 2 would drop out under vibration or movement, triggering the “Check Power System” warning in the BYD car. I repaired the terminal by soldering it securely and reassembled the connector. After a comprehensive road test over 30 km, the fault did not recur, confirming the resolution.
This case highlights the importance of the redundant design in BYD EV accelerator pedal systems. In modern BYD car models, the electronic throttle uses two independent signals to enhance safety and reliability. The primary purpose of this redundancy is to prevent single-point failures that could lead to uncontrolled acceleration or power loss. The ECU continuously monitors both signals for validity through range checks and trend synchronization. Typically, the two signals exhibit an inverse voltage relationship; for instance, at idle, signal 1 might be around 0.5 V while signal 2 is at 4.5 V, and under acceleration, signal 1 rises to 4.5 V as signal 2 falls to 0.5 V. This can be expressed mathematically using linear relationships. Let $$ \theta $$ represent the throttle position as a percentage from 0% to 100%. Then, the voltages can be modeled as:
$$ V_1 = a \cdot \theta + b $$
$$ V_2 = c \cdot \theta + d $$
where $$ a $$, $$ b $$, $$ c $$, and $$ d $$ are constants specific to the BYD EV system. For example, in a standard setup, $$ V_1 = 0.5 + 4.0 \cdot (\theta / 100) $$ and $$ V_2 = 4.5 – 4.0 \cdot (\theta / 100) $$, ensuring that $$ V_1 + V_2 = 5 \, \text{V} $$, a constant sum for validation. The ECU checks if the signals adhere to expected ranges, such as $$ V_{\text{min}} \leq V_1 \leq V_{\text{max}} $$ and $$ V_{\text{min}} \leq V_2 \leq V_{\text{max}} $$, and verifies that their rates of change are synchronized. If discrepancies are detected, the ECU triggers fault codes and may enter a fail-safe mode, reducing engine power to maintain safety.
To further illustrate, consider the ideal signal characteristics in a BYD car throttle system. The table below outlines the expected voltage behaviors under different throttle positions, based on typical BYD EV configurations:
| Throttle Position (%) | Signal 1 Voltage (V) | Signal 2 Voltage (V) |
|---|---|---|
| 0 (Idle) | 0.5 | 4.5 |
| 50 | 2.5 | 2.5 |
| 100 (Full) | 4.5 | 0.5 |
In this specific BYD EV case, the measured voltages deviated slightly from the ideal due to the wiring fault, but the ECU’s validation logic detected the anomaly. The control algorithm can be represented using formulas for error detection. For instance, the ECU calculates a validation value $$ V_{\text{val}} = | V_1 + V_2 – K | $$, where $$ K $$ is a constant like 5 V, and if $$ V_{\text{val}} > \epsilon $$ (a tolerance threshold, e.g., 0.1 V), it flags a fault. Additionally, the rate of change is checked: $$ \left| \frac{dV_1}{dt} – \frac{dV_2}{dt} \right| < \delta $$, where $$ \delta $$ is a small value. Violations of these conditions result in codes like P001D66 and P1D6600, as seen in this BYD car.
Beyond this incident, I have found that BYD EV models are generally robust, but like any complex system, they require meticulous diagnostics. The redundancy in the throttle system is a key feature of BYD car safety, ensuring that even if one signal path fails, the other can provide backup. However, manufacturing defects, such as improper crimping in wiring harnesses, can compromise this design. Regular inspections of connectors and harnesses in BYD EV vehicles are essential to prevent similar issues. In my practice, I recommend using diagnostic tools to monitor live data streams and perform voltage tests during routine maintenance for BYD car owners.
In conclusion, diagnosing power system faults in BYD EV models like the Han DM-i demands a systematic approach that combines code reading, data analysis, and physical inspections. The redundant throttle signal system in BYD car designs is critical for safety, and understanding its principles through formulas and tables aids in effective troubleshooting. This case underscores the importance of attention to detail in electrical connections, as even minor oversights in production can lead to significant performance issues. As BYD EV technology continues to evolve, technicians must stay updated on these systems to provide reliable service and ensure the longevity of these innovative vehicles.