B1CE613 - B1CE613 Rear Fog Lamp Driver Circuit Open Circuit

B1CE613 Rear Fog Lamp Drive Circuit Open Fault Analysis

### H3 Fault Depth Definition

DTC B1CE613 is defined as "Rear Fog Lamp Drive Circuit Open Fault", this diagnostic code performs real-time monitoring on the rear fog lamp actuator loop by the vehicle control strategy system. In the vehicle electrical architecture, the core role of this fault code lies in verifying the integrity of the power transmission path from the domain controller to the rear fog lamp load. The system judges whether there is a high-voltage power interruption or drive path anomaly by monitoring the matching degree between the drive current feedback signal and the expected load state. This definition aims to reveal the closed-loop management logic of the control system for key safety lighting functions, ensuring that under specific configurations (such as R1 platform) and voltage environment ($9V \sim 16V$), the electrical drive loop meets preset normal working standards.

### H3 Common Fault Symptoms

When B1CE613 triggers, drivers or vehicle users will observe the following specific phenomena on instrument display and lighting functions:

• Basic Lighting Status Anomaly: Under near-light operation condition, operating the rear fog lamp switch to "ON" position, the rear fog lamp fails to light up as expected.
• Function Failure Feedback: Although control commands are issued (Switch ON), no effective lighting loop is formed at the rear fog lamp load end, resulting in missing external vehicle lighting signals.
• Diagnostic Information Storage: Vehicle fault monitoring system records this DTC code, usually accompanied by relevant power domain or body domain network status updates.

### H3 Core Fault Cause Analysis

Regarding the underlying electrical architecture of B1CE613, technical level root causes can be analyzed from the following three physical dimensions:

• Hardware Components (Load Side): Rear Fog Lamp Failure. As the ultimate current consumption endpoint, the lamp's internal drive unit, bulb or LED module has open-circuit damage, causing inability to form a closed loop.
• Wiring/Connectors (Transmission Medium): Harness or Connector Failure. This involves wire breakage, insulation layer damage between controller output port and rear fog lamp physical interface, or connector terminal withdrawal, physical open circuit caused by excessive contact resistance.
• Controller (Logic and Drive Side): Left Domain Controller Failure. Internal drive MOS tube open or power management unit abnormality inside the left area controller responsible for outputting control signals, causing inability to deliver effective current to load end.

### H3 Technical Monitoring and Trigger Logic

Control unit determines occurrence of this fault via precise electrical parameter collection algorithm, specific monitoring thresholds and operation condition conditions as follows:

• Drive Current Monitoring Target: System continuously monitors drive current (Drive Current) flowing to rear fog lamp. When controller output command issued, if collected drive current value stays at $0A$ long term, system views it as open circuit feature.
• Time Window Judgment: Fault logic requires within continuous 3s, drive current always remains $0$, during this period system confirms current did not recover or jump.
• Power Supply Voltage Range Limit: Premise for triggering fault determination is system detected controller supply voltage stable between $9V \sim 16V$, ensuring exclusion of power abnormality interference within normal battery voltage range.
• Operation and Environmental Constraints:
  • Gear State: Vehicle must be in "ON" gear (ignition on), system enters self-check or function enable state.
  • Platform Architecture: This fault code logic is only applicable to R1 Platform vehicles, different generations circuit topology exist differences.
  • Configuration Compatibility: Monitoring logic needs to adapt to the following two configuration modes:
    1. Rear tail lamp system independent of LIN bus configuration;
    2. LIN bus rear tail lamp configuration, and rear fog lamp integrated within rear tail lamp assembly integrated system.
• Command Enable State: Basic condition for triggering determination is "Rear Fog Lamp Light Up" command activated by controller, i.e., control end issued conduction signal but no current flow seen.