P2B7300 Technical Specification for Serious Temperature Sampling Open Circuit Fault

Fault Definition

P2B7300 Temperature Sampling Open Circuit Fault (Diagnostic Trouble Code) is a high-priority safety anomaly indicator detected by the Battery Management System (BMS) internal control unit. In this system, this DTC represents that the Battery Intelligent Controller (BIC) has confirmed a serious signal path interruption while monitoring the thermal state inside the battery pack.

From a system architecture perspective, this fault implies an open circuit phenomenon in the physical or electrical connection between the sensor loop responsible for collecting temperature data and the BIC control unit. This fault directly disrupts the feedback loop of the battery thermal management closed loop, causing the control unit to be unable to obtain real temperature data from key battery modules, cooling plates, or the outside wall of the battery pack. When the system judges the sampling channel is in an open wire state, it will be treated as a severe safety event (Severe Fault), forcing entry into protection mode to prevent potential risks caused by ineffective thermal runaway monitoring.

Common Fault Symptoms

Based on original diagnostic data and system feedback logic, specific vehicle-level alarms and functional restrictions are triggered after this fault occurs, including:

• Dashboard Interface Warning: The vehicle dashboard explicitly displays "Powertrain Fault" warning text, indicating that the current drive system is unreliable to the driver.
• Charge/Discharge Function Lockout: The system immediately prohibits battery pack charging input and energy output, preventing the vehicle from driving or recovering energy under fault conditions.
• Auxiliary Power Restriction: If the fault judgment reaches a severe level, it may cause high-voltage relays to cut off, entering the entire vehicle low-voltage system into a restricted power supply mode.

Core Fault Cause Analysis

For the "battery pack internal fault" mentioned in the original data, combined with control unit monitoring logic, a deep attribution analysis is conducted from three dimensions: physical layer and control layer:

• Hardware Component Failure: Temperature sensors inside the battery pack (such as thermistors or thermocouples) may be physically damaged, leading to infinite internal resistance value or direct open circuit; or terminals of connectors inside the battery pack may appear broken, melted, causing signal source loss.
• Wiring and Connector Anomalies: Wires responsible for transmitting temperature signals may be physically disconnected (Open Circuit) due to vibration, compression, or corrosion; BIC pinout retraction, oxidation, or poor contact between plug-in pieces between the BIC and various modules leads to loss of electrical continuity.
• Controller Logic Judgment: Although the BIC control unit itself works normally, its internal ADC analog-to-digital converter processing logic identified abnormal states exceeding the threshold (such as input being an open circuit level), thereby judging that line integrity does not meet safety standards.

Technical Monitoring and Trigger Logic

The generation of this DTC strictly follows preset software logic verification processes, with specific setting conditions and trigger mechanisms as follows:

• Fault Setting Conditions:

  • The temperature sampling signal received by the BIC is continuously monitored to be in an open state within a detection cycle.
  • Precondition Limitations: Must confirm that the Battery Intelligent Controller (BIC) itself functions normally, and false positives are not caused by internal controller logic errors. The fault code is only written when both the BIC is working normally and temperature sampling open circuit conditions are met simultaneously.

• Fault Trigger Conditions:

  • Vehicle Status: The vehicle needs to be in a powered-on state (Vehicle Powered On), at which time high-load calculation modules are activated.
  • Continuous Monitoring Logic: The system scans the BIC's real-time communication link and analog input channels, once confirming $BIC_{normal}$ (BIC working normally) and $Temp_Open = True$ (temperature sampling open circuit), DTC P2B7300 is generated.
  • Data Retention Mechanism: After meeting the above setting and triggering conditions, the fault code will be stored in the BIC control unit's fault memory, and immediately send a "Powertrain Fault" signal to the dashboard, while executing protection strategies prohibiting charge/discharge.