P157216 - P157216 DC Side Voltage Low
Definition of Fault Severity
P157216 fault code in the On-Board Charger (OBC) high-voltage safety monitoring architecture represents a critical electrical state abnormality. This code primarily reflects that the on-board power pack internal high-voltage DC bus bar and converter stage voltage failed to maintain within the normal working range. From the perspective of the control unit (ECU), this fault involves key feedback signal missing or deviation in the communication link between the energy management system (BMS/VCU) and the on-board power. When the system monitors that real-time DC side (DC Side) voltage is below preset electrical safety thresholds, the control strategy will immediately intervene to prevent high-voltage components from overloading or thermal runaway. This fault code is directly related to dynamic monitoring logic in two stages before charging start and after start, serving as the primary basis for judging the health status of on-board power core power stages (such as LLC resonant converter, PFC rectifier unit) and providing real-time feedback on energy supply capability related to motor/battery DC input physical position and rotational speed.
Common Fault Symptoms
When P157216 is stored and activated, the vehicle electronic system will provide clear interactive feedback to the driver, with main symptoms including but not limited to:
- Instrument Warning: The on-board instrument cluster (ICM) displays "Please Check On-Board Charging System" or similar warning icons, indicator light stays on.
- Limited Function: AC charging pile cannot complete handshake authentication, leading to inability to start charging process after plugging/unplugging the charging gun.
- Discharge Prohibition: If vehicle supports external power supply (V2L/V2G), low DC side voltage will trigger protection logic, prohibiting inverter discharge operation.
- System Record: Fault code P157216 is written into on-board diagnostic information storage unit (DTC), and may turn on again after reset based on re-capture conditions.
Core Fault Cause Analysis
According to physical architecture of on-board power pack, triggering of P157216 usually stems from hardware or connection anomalies in the following three dimensions:
- Hardware Components (Hardware): On-board power pack internal failure is the main attribution, possibly involving LLC resonant circuit open, PFC module short circuit failure; additionally, output terminal voltage attenuation or insulation impedance decrease caused by battery pack failure will also directly transmit to DC side monitoring nodes.
- Wiring and Connectors (Wiring & Connectors): Harness or harness connector failure is a common physical inducement, such as high-voltage cable internal break, insulation jacket damage causing leakage current, or DC side connector contact resistance too high causing voltage drop exceeding allowable range.
- Controller: Although less common, analog circuit sampling deviation in on-board power pack control unit may also be judged as voltage abnormality, belonging to potential reasons at system logic operation level.
Technical Monitoring and Trigger Logic
Generation of this fault code follows strict timing monitoring and threshold judgment logic, system continuously collects DC side voltage and compares with safety range:
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Monitoring Target and Value Conditions Control unit monitors two-stage core circuit DC bus voltage in real-time during charging process. Specific physical quantities needing to meet the following inequality relations for setting fault conditions ($V$ is measured voltage, $V_{th}$ is prescribed threshold):
- Before Charging Start Stage: LLC rear-end voltage $V_{LLC} < V_{threshold}$
- After Starting Charging Stage: PFC rear-end voltage $V_{PFC} < V_{threshold}$
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Trigger Logic Flow
- Operating Condition Definition: System needs to detect under two specific operating conditions: charging system initialization (Pre-start) or during charging (During-charging).
- Judgment Condition: Detect any voltage sampling below prescribed threshold, and continuously satisfy monitoring window time requirements, then generate fault code P157216.
- Safety Strategy: Once triggered, system immediately cuts high-voltage contactor control signal to prevent over-current protection failure or power device damage caused by low voltage.
Note: Specific voltage thresholds ($V_{threshold}$) depend on vehicle configuration and on-board power pack specification definition, this explanation only elaborates monitoring principle and general fault logic.
Cause Analysis According to physical architecture of on-board power pack, triggering of P157216 usually stems from hardware or connection anomalies in the following three dimensions:
- Hardware Components (Hardware): On-board power pack internal failure is the main attribution, possibly involving LLC resonant circuit open, PFC module short circuit failure; additionally, output terminal voltage attenuation or insulation impedance decrease caused by battery pack failure will also directly transmit to DC side monitoring nodes.
- Wiring and Connectors (Wiring & Connectors): Harness or harness connector failure is a common physical inducement, such as high-voltage cable internal break, insulation jacket damage causing leakage current, or DC side connector contact resistance too high causing voltage drop exceeding allowable range.
- Controller: Although less common, analog circuit sampling deviation in on-board power pack control unit may also be judged as voltage abnormality, belonging to potential reasons at system logic operation level.
Technical Monitoring and Trigger Logic
Generation of this fault code follows strict timing monitoring and threshold judgment logic, system continuously collects DC side voltage and compares with safety range:
- Monitoring Target and Value Conditions Control unit monitors two-stage core circuit DC bus voltage in real-time during charging process. Specific physical quantities needing to meet the following inequality relations for setting fault conditions ($V$ is measured voltage, $V_{th}$ is prescribed threshold):
- Before Charging Start Stage: LLC rear-end voltage $V_{LLC} < V_{threshold}$
- After Starting Charging Stage: PFC rear-end voltage $V_{PFC} < V_{threshold}$
- Trigger Logic Flow
- Operating Condition Definition: System needs to detect under two specific operating conditions: charging system initialization (Pre-start) or during charging (During-charging).
- Judgment Condition: Detect any voltage sampling below prescribed threshold, and continuously satisfy monitoring window time requirements, then generate fault code P157216.
- Safety Strategy: Once triggered, system immediately cuts high-voltage contactor control signal to prevent over-current protection failure or power device damage caused by low voltage. Note: Specific voltage thresholds ($V_{threshold}$) depend on vehicle configuration and on-board power pack specification definition, this explanation only elaborates monitoring principle and general fault logic.
diagnostic information storage unit (DTC), and may turn on again after reset based on re-capture conditions.
Core Fault Cause Analysis
According to physical architecture of on-board power pack, triggering of P157216 usually stems from hardware or connection anomalies in the following three dimensions:
- Hardware Components (Hardware): On-board power pack internal failure is the main attribution, possibly involving LLC resonant circuit open, PFC module short circuit failure; additionally, output terminal voltage attenuation or insulation impedance decrease caused by battery pack failure will also directly transmit to DC side monitoring nodes.
- Wiring and Connectors (Wiring & Connectors): Harness or harness connector failure is a common physical inducement, such as high-voltage cable internal break, insulation jacket damage causing leakage current, or DC side connector contact resistance too high causing voltage drop exceeding allowable range.
- Controller: Although less common, analog circuit sampling deviation in on-board power pack control unit may also be judged as voltage abnormality, belonging to potential reasons at system logic operation level.
Technical Monitoring and Trigger Logic
Generation of this fault code follows strict timing monitoring and threshold judgment logic, system continuously collects DC side voltage and compares with safety range:
- Monitoring Target and Value Conditions Control unit monitors two-stage core circuit DC bus voltage in real-time during charging process. Specific physical quantities needing to meet the following inequality relations for setting fault conditions ($V$ is measured voltage, $V_{th}$ is prescribed threshold):
- Before Charging Start Stage: LLC rear-end voltage $V_{LLC} < V_{threshold}$
- After Starting Charging Stage: PFC rear-end voltage $V_{PFC} < V_{threshold}$
- Trigger Logic Flow
- Operating Condition Definition: System needs to detect under two specific operating conditions: charging system initialization (Pre-start) or during charging (During-charging).
- Judgment Condition: Detect any voltage sampling below prescribed threshold, and continuously satisfy monitoring window time requirements, then generate fault code P157216.
- Safety Strategy: Once triggered, system immediately cuts high-voltage contactor control signal to prevent over-current protection failure or power device damage caused by low voltage. Note: Specific voltage thresholds ($V_{threshold}$) depend on vehicle configuration and on-board power pack specification definition, this explanation only elaborates monitoring principle and general fault logic.