B2CE655 Adaptive Cruise Control System NVM Configuration Missing Fault Analysis

Fault Depth Definition

B2CE655 (Offline NVM No Configuration Information) belongs to a specific DTC within the Body/Chassis Control Module (CCM) or Dedicated Domain Controller, mainly involving the core initialization data integrity of the Adaptive Cruise Control System (Adaptive Cruise Control, ACC). The core of this DTC lies in the status monitoring of "Non-Volatile Memory" (Non-Volatile Memory, NVM). As a physical module inside the control unit used for long-term storage of key configuration parameters, software calibration data and sensor identification information, its integrity directly relates to the system's self-check logic and function activation. When the system detects that the necessary calibration configuration information is lacking in the NVM area of the front millimeter-wave radar, the control unit determines this as a fault state and records this DTC to ensure the degraded mode in driving safety strategies is correctly triggered. This definition emphasizes that the fault is not simply signal loss, but missing underlying data configuration information, belonging to a logical protection mechanism at the system initialization level.

Common Fault Symptoms

During vehicle operation, drivers and the On-Board Diagnostic System (OBD) will observe the following specific phenomena indicating that the Adaptive Cruise Control System has entered a restricted or disabled state:

• ACC Function Unavailable: The adaptive cruise indicator on the dashboard may not light up, display as an amber warning or show an "unavailable" icon. It cannot activate speed control and following functions through the turn signal lever or steering wheel buttons.
• System Function Failure: The vehicle cannot enter ACC standby state, and the cruise control module cannot read valid target detection data from the radar, causing the system to default to exiting advanced driving assistance mode.
• Fault Light On: The "Adaptive Cruise Control System" or "Millimeter-wave Radar" related warning indicator lights on the dashboard remain on, indicating that current active safety functions are restricted.
• Restricted Driving State: If the vehicle is in a specific calibration mode, the system may force switching to only basic speed cruise (if equipped), and cannot intervene in automatic acceleration/deceleration control.

Core Fault Cause Analysis

For the triggering logic of B2CE655, technical diagnosis needs deep analysis from the following three dimensions, strictly forbidding blind hardware replacement before clearly defining the specific physical state:

• Hardware Component Anomaly: The front millimeter-wave radar itself may have failed, causing internal chips or storage units to be damaged, unable to return valid NVM read data to the main controller (ECC/ACC ECU). Configuration information within the radar module may be lost due to hardware aging, impact or manufacturing defects, making the NVM area present an "no configuration" state.
• Wiring and Connector Connections: Although the fault definition points to NVM, physical layer signal transmission link integrity is equally critical. Communication bus (such as CAN/LIN/High-speed LIN) between control unit and front millimeter-wave radar may experience short circuit, open circuit or high impedance faults, causing main controller unable to correctly parse configuration status information from radar NVM.
• Controller Logic Operations: When the vehicle's internal ACC control unit (ECU) executes self-check logic, if its internally stored checksum does not match received configuration data, it may incorrectly judge "no configuration information". Additionally, software version incompatibility or calibration files failing to successfully write to NVM in the "offline" stage will also trigger this logical condition.

Technical Monitoring & Trigger Logic

The generation of this fault code follows strict hardware and software status monitoring protocols, specific triggering mechanisms as follows:

• Monitor Target: System continuously monitors data integrity of Non-Volatile Memory (NVM) within front millimeter-wave radar module. Main detection indicators include whether stored configuration information exists, checksum matching degree and completeness of sensor calibration parameters.
• Values & Status Thresholds: In fault judgment logic, when NVM configuration information read return results are empty or invalid ID, system triggers alarm. Input data explicitly requires "Offline NVM No Configuration Information", meaning system did not detect expected configuration data structure (such as missing specific Flash area markers).
• Specific Trigger Conditions: Fault is formally recorded and fault light turned on only when Ignition Switch is in ON position electrical system activated state. When ignition signal disconnects, monitoring logic pauses; only after main relay closes with sufficient vehicle power supply, control unit executes read instruction for front millimeter-wave radar NVM configuration. If configuration data missing confirmed at this time, system will immediately write B2CE655 fault code into freeze frame, ensuring maintenance personnel know problem occurred during system power-on self-check phase.