P157100 - P157100 High Voltage Output Open Circuit Fault

Fault Depth Definition

P157100 High Voltage Output Open Circuit Fault is a key diagnostic Trouble Code (DTC) defined in the vehicle's on-board high voltage control system. The core function of this code lies in monitoring the integrity and insulation status of the vehicle's high voltage architecture. In this vehicle series' electrical logic, this trouble code is directly linked to the detection capability of high voltage output busbar fault and the judgment mechanism of on-board power assembly fault.

From a system control perspective, the existence of this DTC is designed to ensure high-voltage current flows along designated load paths, preventing abnormal current return to the chassis or vehicle body shell (i.e., ground wire leakage). It belongs to a critical link in insulation monitoring and circuit integrity protection, used to provide real-time status information about high voltage architecture safety to the whole-vehicle controller. Once the system determines a physical break in the high-voltage output busbar or an abnormal conduction path exists, the P157100 trouble code is immediately activated.

Common Fault Symptoms

When trouble code generation is triggered and stored in the control unit memory, drivers may observe the following driving experience feedback:

• Dashboard warning lights illuminate: Red powertrain warning light or high voltage system indicator lights up continuously, indicating the vehicle is in a safety protection state.
• Vehicle performance limited: Drive motor torque is restricted, vehicle enters "Limp Home Mode" (Failure Protection Mode), maximum speed is locked or acceleration is unavailable.
• High voltage power-off response: In certain conditions, the on-board power assembly may cut off high voltage output, causing the vehicle to momentarily lose drive power.
• Auxiliary functions fail: Auxiliary equipment relying on high-voltage electricity (e.g., AC compressor, PTC heater) stops working, but the low-voltage lighting system usually remains normal.

Core Fault Cause Analysis

According to the fault logic model, the root causes of P157100 can be summarized into three dimensions: hardware component physical damage and electrical connection anomalies:

• Hardware Components (Busbar & Assembly): high voltage output busbar fault is the main hardware trigger. This includes conductor breakage of the busbar itself, insulation layer aging leading to breakdown leakage, or abnormal output voltage and load open circuit/short circuit caused by internal component damage in the on-board power assembly.
• Wiring & Connectors: High-voltage cables compressed within wire slots causing breaks, or high-impedance connections caused by connector pin retraction or terminal corrosion. Such physical connection issues hinder normal current paths and are interpreted by the system as "open circuit" or insulation failure.
• Controller (Controller Logic): Control unit internal monitoring sampling circuit drift, or software logic errors leading to misjudgment of normal voltage fluctuations as leakage states. However, given this code is mainly associated with physical leakage, hardware failure possibilities are far greater than logical calculation errors.

Technical Monitoring and Trigger Logic

The system runs monitoring procedures under specific conditions via specific algorithms, with the following judgment logic:

• Monitoring Target: System real-time monitors high-voltage busbar-to-ground insulation resistance values, output loop current and voltage waveform characteristics.
• Specific Conditions: The key premise for fault judgment is the vehicle discharge state. This means monitoring is effective only when the on-board power assembly is in an active mode of actively powering outwards (e.g., driving motor, starting load) or passively discharging (e.g., load management). During high-voltage power-on self-check or static sleep stages, this trouble code usually does not trigger.
• Trigger Logic: The control unit continuously calculates the ratio of leakage current to standard insulation thresholds. When abnormal current flowing through non-expected paths is detected under a discharge state, it confirms discharge system leakage. Once real-time data exceeds preset safety critical values, the system immediately marks it as a fault and generates the P157100 trouble code, while simultaneously illuminating the fault indicator light to warn drivers and maintenance personnel.