P157400 - P157400 Power Supply Equipment Fault

P157400 Supply Equipment Failure Detailed Definition

In the vehicle high-voltage electrical architecture, P157400 Supply Equipment Failure (Supply Equipment Failure) is a key diagnostic code in the charging management system. This DTC indicates that the Vehicle Power Management Control Unit (PMSCU) has failed to monitor the input status of the AC charging circuit. When the vehicle is in charging mode, the system must verify whether AC power from the grid is successfully transmitted to the On-Board Charger (OBC) or external power interface. The core of this fault lies in the "Supply Equipment" functional group, which covers the integrity of the pre-stage circuitry from the output at the charging pile, through connecting cables, up to entering the vehicle-side high-voltage port. Fault determination means the control unit failed to receive voltage energy feedback conforming to expectations, thus determining a blockage or anomaly in the upstream power supply link.

Common Fault Symptoms

When the diagnostic system determines generating P157400 DTC, the vehicle will show the following perceptible phenomena or instrument feedback:

• Charging Function Failure: Dashboard and central control screen explicitly display "Unable to Charge" status; on-board power interface stops working.
• Charging Indicator Abnormality: Charging port indicator light extinguishes or flashes specific fault prompt mode, no longer showing normal charging in-progress status (usually green steady on).
• Charging Current Interruption: If AC charging is in progress, the charging pile output end may have no current response; system immediately cuts off high-voltage charging circuit to prevent equipment damage.
• System Protection Mode Activation: Charging control unit enters safety protection logic, shielding related power devices to wait for driver intervention or system reset.

Core Fault Cause Analysis

Based on fault code parsing data, the root of this problem is mainly classified into hardware or electronic logic anomalies in the following three dimensions:

• Power Hardware Components：
  • External Charging Connection Device Failure: Refers to physical interface and cable components connecting vehicle and external grid having physical damage, internal contact burning or insulation performance degradation.
  • On-Board Charger Internal Fault: Refers to input rectifier circuit, power devices or control board inside On-Board Charger (OBC) module experiencing hardware damage, leading to inability to handle input AC power.
• Wiring & Connectors：
  • Wires between connection device and control unit have open circuit, short circuit or ground/zero interference.
  • S2 Switch (charging enable or connection detection switch) contacts poor contact or signal transmission blocked.
• Controller：
  • Voltage sampling circuit of vehicle BMS (Battery Management System) or OBC controller drifts, leading to inability to correctly identify AC voltage input signals.
  • Logic operation unit judgment rules triggered abnormally, erroneously generating DTC under specific inputs.

Technical Monitoring & Trigger Logic

The determination of this DTC is based on strict temporal logic and voltage threshold verification mechanism, specific monitoring process as follows:

1. Monitored Target Signals

• Key Signal: AC Voltage Input (AC grid voltage sampling value).
• Status Flag: S2 Switch Status. This switch usually represents charging handshake or connection confirmation signal.

2. Set Condition System logic triggers recording when satisfying complete link below:

1. Vehicle enters AC charging mode.
2. Driver or external device action makes Close S2 Switch.
3. Control unit starts timer, waiting for Specified Time window.
4. Within Specified Time, high-voltage sampling circuit does not detect effective AC Voltage Input.

3. Trigger Condition Once above set process is satisfied, system immediately executes fault determination:

• Operational Constraint: Monitoring only when vehicle in AC Charging State (Vehicle AC Charging State), excluding false alarms during parking or non-charging modes.
• Determination Logic: If after Close S2 Switch and waiting Specified Time, system still does not confirm existence of AC Voltage Input signal, immediately generate P157400 DTC, and store fault to diagnostic memory.

This trigger mechanism ensures reporting fault only when actual charging attempt fails, not occasional fluctuation interference when vehicle off or unconnected power state.