P15FF00 - P15FF00 Internal Temperature Sensor Fault

In-depth Definition of P15FF00 Internal Temperature Sensor Fault

P15FF00 is a critical diagnostic trouble code (DTC) in the high-voltage electrical system of electric and hybrid vehicles, this code clearly points to abnormalities in the internal monitoring loop of the On-Board Charger (OBC) control unit. In the system architecture, the OBC is responsible for converting AC power into DC power for storage in the battery pack, while the internal temperature sensor is a key execution component of the thermal management system. Its core role is to provide real-time feedback of physical temperature data and rotational status inside the OBC module to the control unit. When the control unit receives analog or digital signals from the sensor that do not correspond to the predetermined thermal model, it is judged as "Internal Temperature Sensor Fault". This code implies that the thermal protection strategy of the On-Board Charger may be ineffective, belonging to a key safety warning in vehicle-wide high-voltage power management.

Common Fault Symptoms

Based on the abnormal state of the OBC components, drivers and BMS (Battery Management System) can usually perceive the following driving experience feedback:

• Dashboard displays yellow/red warning lights related to On-Board Charger (OBC) or high-voltage systems lighting up.
• When the charging interface is in AC/DC mode, connection fails or plug-and-play recognition failure occurs.
• Battery power charging power is restricted, showing intermittent interruption of charging phenomena.
• Vehicle enters fault protection state, prohibiting high-power energy injection on DC fast charging piles.
• OBC cooling fan may abnormally start or stop working (accompanied by overheat warning).

Core Fault Cause Analysis

Regarding the fault logic of P15FF00, systematic attribution needs to be made from the following three hardware and electronic dimensions:

• Hardware Component Failure: Temperature sensing elements inside the OBC (such as thermistors or integrated ICs) undergo physical aging, drift, or open/short circuit damage, failing to output effective signals.
• Line and Connector Status: High-voltage side or low-voltage side wiring connecting the sensor to the control unit internal circuit has poor contact, harness wear insulation layer damage, or connector terminal corrosion causing unstable signal transmission.
• Controller Logic Operation Abnormality: The MCU of the OBC main controller chip makes calculation errors in processing input signals from the sensor, calibration parameters are lost, or storage failure occurs, preventing correct parsing of temperature values.

Technical Monitoring and Trigger Logic

The OBC control unit continuously samples the sensor output through a dedicated ADC (Analog-to-Digital Converter) module, specific judgment logic as follows:

• Monitoring Target: Primarily monitors the analog signal voltage value or digital count value output by the sensor, which directly maps to internal junction temperature.
• Trigger Threshold Range: The system compares measured values with calibration range during initial self-check and charging operation conditions. When signal voltage is detected below lower threshold $V_{min}$ or above upper threshold $V_{max}$ (specific limits based on vehicle ECU configuration), it is judged as out-of-range.
• Specific Condition Logic: Faults are not limited to static monitoring; during dynamic monitoring processes where the OBC drive motor (DC side energy conversion) is activated, if compliant feedback signals according to thermodynamic laws cannot be obtained continuously for a set period (e.g., 50 milliseconds to several seconds), P15FF00 will be immediately recorded and freeze frame data stored to trigger safety shutdown mechanism.