P157A37 - P157A37 Charging Grid Frequency High

Definition of Fault Depth

DTC P157A37 is a key diagnostic code regarding the On-Board Charger (On-Board Charger, OBC) monitoring in EV charging systems, its core definition being "High Charging Grid Frequency". This code reflects the vehicle's system monitoring result for input AC parameter stability when the vehicle AC charging interface is connected to the external grid. At the electrical architecture level, the On-Board Charger serves as the core control unit for AC/DC conversion, needing real-time synchronization with the grid power frequency to ensure the stability and safety of the power conversion circuit. The generation of this fault code means the Control Unit (Control Unit) judges that the current AC grid frequency parameters have exceeded the system preset safety logic range, triggering a protection mechanism to prevent power electronic components from undergoing resonance, overheating or mis-triggering protection logic due to excessive frequency fluctuations.

Common Fault Symptoms

When DTC P157A37 is stored and related fault indicator lights are illuminated, vehicle drivers and charging facilities will typically observe the following clear system status feedback:

• Charging Function Fully Locked: In AC (AC) charging mode, the On-Board Charger stops power conversion, leading to an inability to perform any charging operation.
• Charging Current Interrupted: Even when a charging gun is connected and the charging port indicator light is on, the actual battery charge supplement entering is zero; the dashboard charging status may display as "Fault" or "Standby".
• System Protection Activated: The vehicle power management system actively cuts off the input relay to prevent potential damage, manifested by normal charging port locking mechanism but unable to establish an electrical connection.

Core Fault Cause Analysis

Based on original data and vehicle electronic architecture principles, the trigger logic for this fault code mainly attributes to technical factors in the following three dimensions:

• Hardware Component Anomaly: On-Board Charger Internal Fault. Frequency detection circuits, sensors or power components (such as MOSFET/IGBT) inside the vehicle power module suffer physical damage, causing the system to erroneously read high-frequency signals, or the actual grid frequency is normal but the controller misjudges.
• Circuit and Environmental Conditions: High Charging Grid Frequency. The external AC supply network itself experiences fluctuations or specific regional grid instability, leading to input frequency values exceeding the vehicle's allowed operation window. This belongs to electrical characteristic anomalies on the environmental side.
• Controller Logic Judgment: Control Unit (VCU/OBC Controller) frequency sampling threshold setting. Although original data mentions "specified valve threshold", this dimension also involves logical operation of fault judgment, that is, when monitoring frequency signals continuously meet triggering conditions, the system executes logic storage instruction to write fault codes.

Technical Monitoring and Trigger Logic

The On-Board Charging System sets a clear dynamic monitoring mechanism for this fault code, with its judgment logic strictly based on the following technical indicators:

• Monitoring Target: Real-time monitoring of instantaneous frequency signals at the AC grid input terminal.

• Trigger Conditions: Only starts high-frequency detection and fault judgment procedures when the vehicle is in an AC Charging State. This code will not activate under DC discharge or when no charging gun is inserted.

• Value Judgment Logic: The system continuously samples grid frequency parameters, and once the detected AC grid frequency $f_{grid}$ satisfies the following inequality relation, it triggers fault code generation:

  $$ f_{grid} > f_{threshold} $$

  Where, $f_{threshold}$ is the system-specified frequency threshold. This logic aims to ensure that under dynamic operating conditions of drive motors or battery charging, the power conversion system always operates within the designed frequency range, avoiding instability in the internal topology structure of the On-Board Charger due to excessively high grid frequency.