P157016 AC Side Low Voltage Fault Technical Documentation

Fault Definition

P157016 is a key diagnostic parameter used in the On-Board Charger (OBC) control system for monitoring AC input power quality. When the vehicle's Energy Management System performs an external power supply handshake procedure, the control unit continuously collects AC side input voltage signals and compares them with preset safety thresholds. The core function of this DTC is to protect the high-voltage power conversion module inside the On-Board Charger. It prevents forced charging when input power fluctuation exceeds design specifications, thereby avoiding thermal overload damage or logic crash risks for inverter circuits, rectifier bridges, and capacitor components. Its monitoring target is the line voltage signal at the vehicle AC entry, ensuring the power supply environment meets the electrical conditions for normal OBC operation.

Common Fault Symptoms

After the P157016 DTC is written into the control memory, the driver and related systems receive feedback through the following perceivable phenomena:

• Charging Function Interruption: Communication handshake failure between the vehicle and external power source, leading to inability to start AC charging or premature termination of the charging process.
• Dashboard Warning Trigger: The charging fault indicator light illuminates on the instrument cluster, possibly accompanied by general fault prompts from the Low Voltage or Battery Management System.
• Charging Icon Anomaly: Stalled increase in remaining battery display or unstable power connection status on the screen/instrument. The system enters a protection standby mode.

Core Fault Cause Analysis

According to the diagnostic logic system, potential failure mechanisms leading to this DTC generation are categorized into the following three dimensions:

1. Hardware Component Failure

   • External Power Supply Interface: Physical damage to the high-voltage conversion module, power factor correction circuit, or voltage regulation unit inside the EVSE (Electric Vehicle Supply Equipment), preventing stable voltage output.
   • On-Board Charger Unit: Aging input filter capacitors, rectified diode breakdown, or performance degradation of PFC stage circuit components within the vehicle-side OBC, causing equivalent voltage monitored on the input side to be below normal levels.

2. Line and Connector Connection Status

   • High Voltage Input Impedance Anomaly: Poor contact in long-distance power cables or gun lines from the grid to the vehicle, causing excessive voltage drop during current transmission, resulting in endpoint detection voltage below specified values.
   • Power Quality Fluctuation: Transient dips or long-term low-voltage operation intervals at the external grid source; the voltage signal passed through the AC charging gun interface into the vehicle control unit fails to meet startup logic requirements.

3. Controller Logic Calculation and Threshold Management

   • Monitoring Algorithm Deviation: Abnormalities in ADC conversion of AC input voltage sampled by the OBC internal MCU, causing calculated instantaneous or average voltage to be lower than real values.
   • Protection Strategy Trigger: The system control unit determines based on preset safety logic that current input power level does not meet safe startup conditions, thus actively generating the DTC to lock output status.

Technical Monitoring and Trigger Logic

The trigger mechanism for this DTC relies on real-time dynamic sampling of AC side input voltage signals. Specific monitoring parameters and trigger conditions are as follows:

• Monitoring Target

  • RMS Voltage of AC lines at the vehicle high-voltage entry ($V_{AC_input}$), including line-to-line and phase voltage sampling.

• Numeric Judgment Logic

  • The system has an internal voltage protection lower limit threshold, defined as $V_{threshold}$.
  • Trigger condition is when real-time input voltage monitored continuously remains below this limited value: $$ V_{AC} < V_{threshold} $$
  • Where, $V_{threshold}$ is the specified valve defined by the vehicle manufacturer in the control unit calibration program.

• Specific Operating Condition Requirements

  • Trigger detection occurs only during the startup phase after vehicle power-on (Vehicle Power-On) and during charging connection processes.
  • When the system detects AC voltage below the specified threshold, a DTC is generated and the charging circuit is locked.