P15794B - P15794B Temperature Sampling 1 High

P15794B Fault Depth Definition

In an EV On-Board Charger (OBC) system, fault code P15794B corresponds to a specific temperature sampling logic anomaly, specifically pointing to "Transformer Temperature Sampling 1 High". This fault code indicates that the vehicle's electronic electrical architecture has detected critical power conversion components—the high-frequency transformer—where its feedback real-time thermal status data exceeds safety thresholds. Within the system's Control Unit (Control Unit), this signal is a core input variable in the thermal management closed-loop feedback loop. When the controller determines the transformer temperature value collected is abnormally high, the system identifies it as an overheating risk, thereby triggering protection mechanisms to prevent power device insulation failure or core demagnetization due to long-term operation in a high-temperature environment. The occurrence of this fault code is usually associated with thermal stability assessment logic of the OBC Module and is one of the key indicators for judging the overall vehicle charging thermal safety level.

P15794B Common Fault Symptoms

When system judges P15794B fault holds true, user end or diagnostic terminal will observe significant changes in vehicle electrical behavior. Specific driving experience manifestations and dashboard feedback are as follows:

• Vehicle cannot accept external AC power charging, charging interface indicator light extinguishes or reports error;
• Outward discharging function (such as V2L Vehicle-to-Load) is forcibly prohibited by system, socket power supply output cut off;
• Vehicle onboard instrument shows relevant fault information or charging management warning icon lights up;
• Charging pile communication handshake successful but power cannot increase, maintain in initial standby state;
• Vehicle enters energy saving protection mode, BMS with OBC communication interaction indicates thermal protection lock.

P15794B Core Fault Cause Analysis

Analysis of main causes for this fault code based on hardware system architecture can be technically analyzed from the following three dimensions:

Hardware Component Abnormality

• Coolant Circulation Failure: Lack of coolant leads to insufficient medium in flow channel, unable to effectively carry away Joule heat generated by transformer, causing local temperature rise to quickly exceed safety threshold;
• Water Pump Malfunction: Water pump in cooling loop mechanically stuck or motor drive failure, causing coolant flow rate too low or stagnant, heat exchange efficiency significantly reduced;
• Fan Malfunction: OBC module external forced air cooling component (fan) appears unstable speed or stop rotation, leading to insufficient convective cooling capability;
• OBC Internal Fault: Transformer winding aging, insulation layer damage or PCB board thermal stress damage, causing device itself heat dissipation abnormal increase.

Wiring and Connector Physical Connection

• Sensor Signal Transmission Harness: Transformer temperature sensor power supply line or grounding circuit exists contact resistance too large, loose connection or open circuit phenomenon;
• Connector Oxidation Corrosion: Under high-temperature environment metal contacts oxidize or dust accumulation, leading to collected analog signal appearing offset or interference by noise.

Controller Logic Computation

• Thermal Protection Strategy Threshold Setting: Thermal management algorithm parameters inside control unit drift or misjudge, trigger protection prematurely before physical overheating;
• Data Acquisition Module Fault: ADC (Analog-to-Digital Converter) sampling circuit accuracy abnormal, causing original analog voltage value incorrectly converted to high temperature data.

P15794B Technical Monitoring and Trigger Logic

System monitoring logic for this fault is based on specific working conditions and real-time data judgment, specific trigger conditions as follows:

• Monitoring Target OBC Control Unit real-time collects transformer winding or core area temperature sensor signal, focus monitor sampling value absolute numerical and rate of change with time. Mainly concerned about signal voltage corresponding physical temperature whether enter overheating zone.
• Numerical Judgment Range System sets strict safety threshold as criteria. When detecting transformer temperature sensor collected value $T_{sensor}$ satisfies following inequality relationship, considered fault triggered: $$ T_{sensor} > T_{threshold_specified} $$ (Note: $T_{threshold_specified}$ is control system internal preset regulation valve).
• Specific Trigger Conditions This fault judgment only valid under specific working modes interacting with external grid. Specifically includes the following two states: 1. Vehicle AC Charging Mode (AC Charging Mode): When OBC in process charging from grid to power battery; 2. Vehicle Outward Discharge Mode (V2L Mode): When system open V2L function, outward load power supply when. Only under above two conditions, if monitoring transformer temperature sensor feedback data exceeds regulation valve value, system immediately interrupts power loop and generates P15794B fault code, enter safety lock mode.