P158F16 - P158F16 High Voltage Side Input Undervoltage During Discharge

P158F16 Fault Code Detailed Definition

In the electric vehicle high-voltage electrical architecture, P158F16 (High Side Input Under Voltage during Discharge) is a critical protective fault code configured for the energy output stage by the on-board power system. The primary function of this fault code involves real-time monitoring of high-voltage bus voltage stability supplied to drive loads while the vehicle performs discharge tasks (such as external power supply, V2L functionality, or energy release under specific conditions). The control unit continuously collects high-voltage input signals and compares them with specified thresholds, aiming to ensure that the power system maintains normal energy conversion efficiency and output quality under dynamic high-load conditions. The generation of this fault code is directly linked to the system's identification of high-side input under-voltage states, serving as a crucial diagnostic basis to prevent equipment damage or safety hazards caused by insufficient power supply.

Common Fault Symptoms

When the P158F16 fault condition is activated, the on-board control system triggers corresponding protection logic. The driving experience and dashboard feedback perceptible to owners primarily manifest as:

• Function Limitation: The vehicle cannot perform discharge output normally; the system may completely disable the discharge function.
• Dashboard Display: The high-voltage alarm light or power management warning light on the instrument cluster illuminates, indicating abnormal high-side input voltage.
• System Logs: The on-board diagnostic system (OBD) records this fault code and is typically accompanied by a clear status identifier of "Unable to Discharge".

Core Fault Cause Analysis

Based on raw data feedback and system architecture logic, P158F16 faults can be categorized and analyzed for investigation from the following three dimensions:

• Line or Connector Faults: Wiring connected to the high-side input terminal may suffer damage, insulation aging, or connector contact issues, leading to signal transmission interruption or abnormally increased resistance, causing distortion in input voltage monitoring.
• Hardware Component Faults: Primarily includes faults within the battery pack itself and internal faults of the on-board power assembly. As high-power energy sources and conversion units, internal cell inconsistency deviations or module-level circuit damage within these components can directly result in output-side voltage failing to meet specified requirements.
• Controller (Logic Operation): While primarily involving hardware connections, controller threshold monitoring logic is equally critical. Technically, faults internal to the on-board power assembly may involve anomalies in sensor acquisition circuits or controller processing logic, requiring further judgment via data streams to determine if there is a physical power shortage or detection signal false alarm.

Technical Monitoring and Trigger Logic

The triggering of this fault code follows a strict dynamic monitoring mechanism, with specific logic as follows:

• Monitoring Target: High-side input voltage signal when the vehicle is in discharge mode.
• Value Range Definition: System judgment occurs only under specific dynamic conditions. The core premise for fault determination is that the discharge output current exceeds the specified threshold ($I_{output} > I_{threshold}$). Under static or low-load conditions below this current threshold, even slight voltage fluctuations may not immediately trigger this code.
• Trigger Condition: When the vehicle confirms it is in a discharge state, and the detected input voltage remains continuously below the allowable range while accompanied by discharge output current exceeding the specified threshold, the internal controller of the on-board power assembly will generate P158F16 fault code and lock related functions.
• Specific Conditions: This monitoring logic specifically targets the "Discharge Output" working mode, distinct from vehicle charging or standby states, reflecting the system's requirements for high-load discharge voltage stability ($V_{input} < V_{min_allowable}$ combined with $I > I_{threshold}$).