P1AFB00 - P1AFB00 HVAC System High Voltage Interlock Fault

Fault Deep Definition

P1AFB00 (Air Conditioning System High Voltage Interlock Fault) is a specific DTC diagnosed internally by the Integrated Intelligent Front Drive Controller. In the new energy vehicle electrical architecture, this fault code primarily involves logical verification between the thermal management system and the high-voltage safety control loop. The code indicates that the vehicle control system cannot confirm that the HVAC high-voltage module and related components' High Voltage Interlock Loop (HVIL) are in an effective closed or physically safe state.

The Integrated Intelligent Front Drive Controller, as a core execution unit, is responsible for monitoring HVIL signals. When the system detects HVIL loop failure, the control unit determines that the area has potential safety risks, such as high voltage intruding into the low voltage domain or arc discharge caused by poor connector contact. This fault code is established to ensure that during OBC or HV module power supply processes, all physical interfaces can reliably maintain electrical isolation and connection integrity, preventing high-voltage safety risks due to lost interlock.

Common Fault Symptoms

When the P1AFB00 DTC is triggered and recorded in the control unit, the vehicle will provide specific warning information to the driver to indicate system state abnormalities:

• Dashboard Display "Check Connector": This is the most significant user-visible signal, usually appearing on the multimedia interaction interface of the dashboard or central screen. The prompt explicitly points to a question about the connection status of the HVIL loop and suggests checking the physical state of relevant interfaces immediately.
• HV System Protective Power Reduction: For safety considerations, the control unit may limit HVAC compressor operating power or completely prohibit compressor startup when detecting faults, to avoid high-voltage abnormal loads.
• OBC Work Status Limited: Under specific conditions, if the fault relates to the charging process, users might find the vehicle cannot normally enter charging mode or charging power is significantly limited.

Core Fault Cause Analysis

For technical diagnosis of this DTC, system components need to be inspected from the following three dimensions to ensure no potential hardware or logic level anomalies are missed:

1. Physical Connection Components (Connectors and Wiring)

   • Integrated Intelligent Front Drive Compressor Connector Not Connected Properly: This is the most common physical cause. The HVIL loop depends on mechanical locking in place at each interface. If connectors loosen, terminals retract pins or connections are not fully inserted, it will interrupt the interlock signal.
   • Harness Continuity Anomaly: Connecting lines may exist with open circuits, short circuits, or damaged insulation layers, preventing high potential differences from being correctly fed back to controller inputs.

2. High Voltage Actuator Components (Compressor)

   • Air Conditioner Compressor Fault: The compressor body internally may fail, such as mechanical jamming or internal circuit open, leading to abnormal interlock switch contact status and failing to feedback a correct "closed" signal to the control unit.

3. Control Logic Calculation Unit

   • Integrated Intelligent Front Drive Controller Fault: Sampling circuits, comparators, or software logic inside the controller may become abnormal, causing it to incorrectly determine normal voltage levels as low level, thus falsely reporting the fault code.

Technical Monitoring and Trigger Logic

The system continuously evaluates high-voltage safety status during vehicle operation through preset monitoring strategies. The specific technical determination logic is as follows:

• Monitoring Target Parameters

  • HV Module Voltage: Core monitoring variable used to confirm if there are abnormal power offs or leakage in the high-voltage side.
  • OBC Voltage: As an auxiliary monitoring variable, evaluate the stability of external power input.

• Fault Determination Value Conditions

  • When the above voltage parameters are detected less than the specified threshold ($< \text{Threshold}$), the system will mark it as an abnormal state. The "specified threshold" is pre-set by the controller internal calibration program to define the minimum voltage boundary for safe operation.

• Specific Trigger Conditions

  • Vehicle Powered On: The basic premise for fault determination is that the vehicle power management system has completed power-on initialization.
  • In Discharge Process: This fault activates only when the onboard system is currently undergoing energy management processes (such as charging or discharge modes).
  • Judgment Process: Once "Vehicle Powered On and in Discharge Process" occurs, if real-time collected voltage falls below the specified threshold, the Integrated Intelligent Front Drive Controller will immediately generate P1AFB00 fault code and store it in the fault memory.