Technical Analysis of DTC B1B5D14: Ground Short or Open Circuit on Rear Center Sensor Signal Line

Fault Depth Definition

This fault code B1B5D14 belongs to electrical communication diagnostic information in the vehicle electronic architecture, mainly targeting the rear center radar sensor module of the Parking Assist System. In the vehicle network topology structure, the left domain controller is responsible for receiving data streams from the rear center radar sensor, and the transmission medium of this data stream is the "signal line". When the system detects unexpected electrical states on the signal line — namely "Signal Line Short to Ground" or "Open Circuit" — the control unit determines that the communication link integrity is compromised.

Term interpretation in the fault code:

• Rear Center Sensor: Refers to the radar detection module located at the center rear of the vehicle, responsible for real-time data acquisition of physical position and rotation angle.
• Signal Line Short to Ground: Indicates accidental connection between the signal transmission path and the vehicle ground point, causing signal voltage to be pulled down to zero potential, unable to transmit effective commands or data.
• Open Circuit: Indicates interruption in the physical connection of the signal transmission path (e.g., broken or disconnected), leading to infinite impedance or communication handshake failure.

This fault code reflects the basic physical connection failure between the control system and sensing hardware, belonging to low-level diagnostic information at the electrical system level, directly related to the reliability assurance of the vehicle perception system.

Common Fault Symptoms

When the control unit confirms the existence of B1B5D14 fault, the Parking Assist System will enter a restricted operation mode to protect system integrity. Observable phenomena for owners or technicians include:

• Parking Assist Function Degradation: The parking assist warning lamp on the dashboard lights up, indicating partial function failure (e.g., distance display disappears, audio alerts interrupted).
• User Interface Feedback Abnormalities: The radar scan area on the center screen shows missing or error messages, unable to display real-time state of obstacles behind the vehicle.
• System Entering Safety Protection State: If signals continue to be abnormal, the system may completely disable the rear center radar's transmit and receive functions to avoid false positives.

Core Fault Cause Analysis

Based on keywords in the fault description, this fault can be systematically divided into the following three potential hardware or logic sources across technical dimensions:

• Hardware Component Layer: Rear Center Radar Sensor Failure. Damage occurs in the transceiver circuitry, signal processing chip, or communication interface IC inside the sensor, preventing generation of effective modulated signals.
• Wiring/Connector Layer: Harness or Connector Failure. This is the most common physical cause, possibly involving insulation layer damage leading to ground contact, or plug internal pin oxidation/loosening causing open circuit. Additionally, wire breakage caused by external mechanical interference/squeezing is also a common trigger.
• Controller Logic Layer: Left Domain Controller Failure. Although the fault description points to the signal line, if the receiving circuit on the controller side has power fluctuations, failed signal filtering modules or logic interpretation errors, it may also misreport this communication fault.

Technical Monitoring and Trigger Logic

The control unit's determination of this fault follows strict timing and electrical threshold logic, specific monitoring strategies as follows:

• Monitoring Target: System continuously monitors the status of signal lines connected to the rear center radar, including signal voltage levels and communication protocol integrity. Focus on detecting whether the line is abnormally biased towards ground potential or presents a high impedance open circuit state.
• Trigger Condition: The specific environmental condition for fault determination is "Ignition Switch in ON Position". At this time, the control unit initialization is completed and enters active monitoring mode, starting periodic sampling of sensor inputs.
• Judgment Logic: Under ignition on condition, the control unit compares received signal features with preset normal ranges in real time. If signal voltage is detected to remain within non-effective communication windows (e.g., low level during short or high impedance state during open circuit) for a period exceeding threshold setting, the system will record fault code B1B5D14 and freeze related function outputs.