B134713 - B134713 AC Pressure Sensor Open Circuit

Technical Analysis of DTC B134713 A/C Pressure Sensor Open Circuit

Fault Definition Depth

In the vehicle thermal management system architecture, DTC B134713 specifically points to a key sensing component in the high-side protection circuit of the AC compressor. As a core actuator for closed-loop feedback in the system, the A/C pressure sensor's core function is to monitor the pressure status of the refrigerant circulation system in real time. When the system identifies that the signal output from this sensor deviates abnormally from preset logic, the control unit judges it as an "open circuit" or signal source anomaly (Signal Deviation). This fault code essentially diagnoses damage to the physical connection or electrical signal integrity between the A/C pressure sensor and the control system, which may cause the domain controller to be unable to obtain accurate refrigeration operating data, potentially triggering a protection mechanism to prevent compressor over-pressure damage.

Common Fault Symptoms

Since the AC system uses multi-redundant control logic, a single sensor anomaly may lead to function degradation rather than immediate failure. Below are the driving experience feedback perceivable by owners and specific manifestations on the instrument panel:

• Partial A/C System Function Failure: The compressor may frequently disengage operation or fail to load the refrigeration cycle normally according to instructions.
• Instrument Warning Lights On: "Check A/C" or fault indicator lights related to pressure sensors will appear in the vehicle information system, entering service mode.
• Abnormal Cool Air Output: Under specific operating conditions (such as rapid acceleration or high heat load), the cabin temperature regulation capability decreases, and heating and cooling confusion occurs.
• Control Strategy Restrictions: The electronic control system may automatically limit the output power of the AC system to protect core compressor components.

Core Fault Cause Analysis

Based on electrical architecture and system logic, the fundamental causes leading to the generation of this fault code can be precisely classified into the following three technical dimensions:

1. Hardware Component Failure: A/C Pressure Sensor Failure. This usually refers to permanent damage to sensitive elements or signal conditioning circuits inside the sensor, resulting in inability to output expected voltage corresponding to physical pressure.
2. Line and Connector Anomalies: Harness or Connector Faults. Involves issues regarding the physical integrity of the signal transmission path, including pin corrosion, excessive contact resistance in connectors, wire insulation damage leading to power short circuits, etc.
3. Controller Logic Computation Deviation: Left Domain Controller Failure. Refers to internal reference voltage drift or signal acquisition circuit anomalies in the central computing unit responsible for processing this sensor's input signals, misjudging normal physical signals as open state.

Technical Monitoring and Trigger Logic

The diagnostic algorithm of the vehicle electronic control system performs real-time monitoring based on specific electrical thresholds, with its judgment logic as follows:

• Monitoring Target: Analog output voltage of the A/C pressure sensor. The system continuously monitors the DC signal level feedback from the sensor to the control port.
• Voltage Threshold Standard: When the detected sensor output signal voltage is stable above $4.95V$, the system judges it as a high signal state beyond normal operating range. In a typical ground reference architecture, this voltage value usually corresponds to open or short circuit fault characteristics.
• Trigger Operating Conditions: This fault judgment is effectively monitored and logically operated only when the ignition switch is in the ON position (Ignition Switch ON Position). When the system is in this state and meets the above voltage threshold conditions, the fault code will formally enter storage status and turn on the instrument warning light.