P159017 - P159017 AC Side Output Overvoltage During Discharge

Detailed Fault Definition

DTC P159017 (On-Board Power Unit Overvoltage on AC Side during Discharge) is a significant event marker in vehicle power system diagnostics, specifically used to indicate the abnormal status of the On-Board Power Unit under specific operating modes. The core definition of this fault code involves voltage threshold protection mechanisms during the energy conversion process: if the control system identifies that the system is in discharge mode (Discharge Mode), meaning the moment when the onboard battery outputs electrical energy to external loads or the AC grid, and if the detected voltage value at the AC Side output terminal exceeds the preset safety baseline, the system will immediately record this DTC. In the technical architecture, this fault code reflects the dual management function of the control unit on power quality and safety boundaries, belonging to the direct feedback result of the internal integrated monitoring logic of the On-Board Power Unit, indicating that the high-voltage energy management system failed to maintain normal output voltage stability.

Common Fault Symptoms

When DTC P159017 is triggered, users or diagnostic equipment can typically observe the following specific system responses and driving experience abnormalities:

• Dashboard Warning Indicator Illuminates: The central instrument screen may show warning icons related to the high-voltage system or power management lighting up, indicating that the vehicle is in an abnormal power supply state.
• Onboard AC Power Functionality Failure: The 220V/110V AC outlet (such as a V2L discharge interface) located at the rear or inside the vehicle will stop outputting electrical energy and cannot supply power to external appliances.
• Power Output Limited or Interrupted: Since the On-Board Power Unit is judged to have internal fault risks, the vehicle management system may limit battery discharge power, or even temporarily interrupt the high-voltage system operation to prevent potential damage.
• Abnormal System Reset Status: When reading on specific maintenance diagnostic equipment, this fault code usually does not clear automatically with the ignition cycle, requiring connection of a professional diagnostic tool for resetting frozen frame data and code storage.

Core Fault Cause Analysis

Based on the "On-Board Power Unit Internal Fault" indicated by existing raw data, combined with vehicle electronic system architecture principles, the logical root causes of this fault can be broken down into the following three core dimension potential physical mechanisms:

• Hardware Component Level: The main power stage circuit of the On-Board Power Unit (such as inverter bridge arms, rectifier modules or filter capacitors, etc.) undergoes performance degradation, breakdown or aging, resulting in inability to effectively control bus voltage fluctuations during the physical process of converting DC electrical energy to AC electrical energy.
• Wiring and Connector Level: There is a risk of insulation layer damage in the high-voltage wiring bundle inside the unit assembly, or critical test points on internal PCB boards, sensor feedback circuits appear with cold solder joints, breaks, or excessive contact resistance, leading to inaccurate voltage signal sampling values or abnormal overshoot at actual output terminals.
• Controller Logic Calculation Level: Internal algorithm threshold judgment deviations of the On-Board Power Control Unit (PCU), its monitoring module fails to make protective cut-off instructions in time when voltage instant fluctuations exceed critical values, or internal memory regarding voltage protection curve calibration data exists abnormalities.

Technical Monitoring and Trigger Logic

The system's determination of this fault code strictly follows preset dynamic monitoring processes, with specific technical logic as follows:

• Monitoring Target: Focuses on collecting instantaneous voltage signals ($V_{AC}$) at the AC Side output terminal and power conversion status parameters related to it. The monitoring process continues only during the On-Board Power Unit executes discharge operations (Discharge Mode), not triggered in silent or charging modes for this specific determination.
• Value Range and Threshold Judgment: The control unit calculates in real-time the collected output voltage value $V_{measured}$ and the preset maximum safe threshold $V_{threshold}$. Once the condition of $V_{measured} > V_{threshold}$ occurs continuously within monitoring cycles, the system determines it as an overvoltage event.
• Fault Trigger Logic: When output overvoltage is detected and the duration exceeds the minimum window period allowed for diagnostics, the Electronic Control Unit (ECU) will illuminate the fault indicator light, lock related power device drive signals, and record DTC P159017. This mechanism aims to ensure that the On-Board Power Unit does not send voltage energy exceeding tolerance limits to AC side loads under extreme operating conditions, guaranteeing the safety integrity of grid interfaces and external devices.