P157017 - P157017 AC Side Voltage High

In-depth Fault Definition

P157017 "AC Side Voltage High" is a critical Diagnostic Trouble Code (DTC) for the On-Board Charger System (OBC), playing a core role in monitoring electrical safety at the high-voltage input. This fault code reflects the failure of the vehicle control unit's real-time parsing capability of the AC Side Voltage signal. In the feedback loop of the charging management system, this code indicates that the grid-side or power-source input voltage received by the control unit exceeds the preset safety logic boundary. This typically means the internal voltage sampling circuit, ADC analog-to-digital converter, or high-voltage control strategy within the on-board power unit cannot maintain normal electrical stability under current operating conditions, triggering the system protection mechanism to interrupt the charging process.

Common Fault Symptoms

Based on analysis of raw data and driving experience correlation, when this fault code is written, users or repair technicians can perceive abnormal vehicle states through the following dimensions:

• Instrument System Feedback: The dashboard clearly illuminates warnings or icons related to "Check On-Board Charger System", alerting drivers to charging safety hazards.
• Loss of Charging Function: The on-board power unit actively disconnects the AC input circuit, preventing AC charging. The charging pile indicator lights usually remain off or display a fault status.
• Charging Connection Interruption: After inserting the AC charging gun, the vehicle cannot enter pre-charge or charge-lock states. Even if the user confirms normal physical connection, the system still refuses to handshake.
• High Voltage Insulation Monitoring Anomaly: Due to threshold exceeded, some models may accompany insulation monitoring system alarms, preventing the high-voltage interlock loop from passing self-checks.

Core Fault Cause Analysis

Based on the judgment logic of P157017 "AC Side Voltage High", decompose the fault source into the following three technical dimensions for diagnosis analysis:

• Hardware Component Faults
  • On-board Power Unit Internal Fault: High-voltage power modules, sampling resistors, or main control chips inside the OBC may age or break down, failing to stabilize voltage or handle over-voltage situations correctly.
  • External Charging Device Fault: The external AC charging station (CCS/Generic CHAdeMO/Standard) itself outputs abnormally or its internal controller is unstable, delivering voltage energy exceeding specifications to the vehicle side.
• Wiring and Connector Faults
  • Harness or Connector Fault: Partial breakdown or insulation damage in the high-voltage charging harness causes leakage interference against ground, or oxidation/loosening of input pins at the high-voltage end changes contact resistance, subsequently causing control unit misjudgment of voltage signals.
• Controller Logic Faults
  • Grid Voltage High (Environment Trigger): Although the grid is not a vehicle component, the OBC internal control strategy or sensor calibration fails to adapt to grid fluctuations in specific time periods, leading the system to judge external input voltage $V_{AC}$ exceeds the "specified threshold" allowed by safety logic.

Technical Monitoring and Trigger Logic

The generation of this fault code depends on continuous monitoring of analog signals by the High-Voltage Control Unit (HV Control Unit), with specific trigger logic as follows:

• Monitoring Target System continuously collects instantaneous voltage signals at the AC input end, processing them via high-precision ADC.
• Value Judgment Condition When the monitored actual AC side voltage $V_{AC}$ continues to exceed the "specified threshold" set internally in the system ($V_{Threshold}$), the control unit starts a fault timer. $$ V_{AC} > V_{Threshold} $$
• Trigger Condition Constraints This fault code is only effectively activated under "Vehicle AC Charging State". That is, only during dynamic monitoring when the high-voltage contactor is closed and the charger enters operation mode does the system execute the above voltage threshold comparison and generate P157017 fault code.