P151100 - P151100 AC Terminal High Voltage Interlock Fault

In-Depth Definition of P151100 AC Side High Voltage Interlock Fault

In New Energy Vehicle (NEV) high-voltage architecture systems, DTC P151100 represents a failure in safety monitoring between the On-Board Charger (OBC) and the AC grid interface. This fault falls under the logic diagnosis category of the High Voltage Interlock Loop (HVIL) system. Its core function is to ensure electrical insulation integrity and connection reliability of the high-voltage loop.

When the on-board charger control unit detects abnormal interlock loop signals from the AC input terminal, the system judges it as an "AC Side High Voltage Interlock Fault". This mechanism is part of an active safety strategy aimed at preventing high-voltage energy delivery to the battery pack or high-voltage busbar if the charging plug is not fully inserted or if external high-voltage connectors are loose or damaged. This DTC is directly related to the monitoring of physical isolation states at the charging interface and serves as a key feedback loop data for the vehicle's power management system regarding the AC side electrical topology status.

Common Fault Symptoms

When the P151100 DTC is written into the control memory, the vehicle's electronic systems will immediately enter protection mode, manifesting as the following perceivable driving experiences and instrument feedback:

• Complete Charging Function Interruption: The vehicle cannot accept AC electric energy from charging piles or home chargers. The charging gun indicator typically shows a fault status, or there is no power signal at the charging socket interface.
• User Interface Error Reporting: "Cannot Charge", "Charger Fault", or related system error messages pop up on the central control screen or instrument cluster, explicitly informing the driver that charging conditions are currently unavailable.
• Charging Process Interruption: If this code is triggered while the vehicle is charging, the charger will immediately stop energy transmission (i.e., cut off output current) and lock the charging port to wait for fault reset.

Core Fault Cause Analysis

Based on fault logic and hardware architecture, the causes of P151100 can be analyzed based on the following three dimensions:

• Line and Connector Physical Connection: Refers to physical failure in the external interlock loop. For example, open or short circuit of the AC side interlock wiring harness, or oxidation of high-voltage connector pin terminals leading to excessive contact resistance, preventing correct signal transmission to the on-board charger control unit.
• On-Board Charger Hardware Components: Refers to physical damage to the circuits inside the On-Board Charger (OBC) responsible for collecting high-voltage interlock signals. For example, open voltage sampling resistors, breakdown of optocoupler isolation devices, or damaged interface chips, causing the controller to be unable to perceive the true state of the interlock loop.
• Controller Logic Operation and Judgment: Involves abnormal processing by the internal control unit of the on-board charger against input signals. When signal voltage waveforms or levels exceed preset logic safety thresholds, the control unit executes fault judgment algorithms and generates P151100 identifier codes.

Technical Monitoring and Trigger Logic

The generation of this DTC follows a rigorous Electronic Control Unit (ECU) self-diagnosis strategy. Its monitoring and trigger mechanism are as follows:

• Monitoring Target: The on-board charger control unit continuously monitors the validity of high-voltage interlock loop signals (Signal Validity). The system focuses on collecting potential level states and logic signal changes within the interlock loop.
• Value Range and Judgment: Under normal operating conditions, the control unit must confirm that the interlock line is in a closed valid state; when an interlock fault signal is detected as valid, it is considered as safety monitoring failure. This process does not involve fixed voltage value settings but performs real-time comparison based on the validity of system logic signals (Logic Signals).
• Specific Trigger Conditions: The necessary condition for DTC generation is "Vehicle AC Charging Status". Only when the charger enters work mode or is ready to receive AC energy, if the on-board charger detects a high-voltage interlock fault signal as valid, the control system will formally generate P151100 DTC and record logs.