B133711 - B133711 Refrigerant Temperature Sensor 3 Short to Ground

Fault Definition Deep Dive

DTC B133711 (Refrigerant Temperature Sensor 3 Short to Ground) represents a critical electrical anomaly in the air conditioning system control strategy. In systems where this fault code exists, Refrigerant Temperature Sensor 3 acts as part of a closed-loop feedback loop, responsible for transmitting real-time physical state data regarding evaporator or specific location temperature to the control unit. The so-called "Short to Ground" means electrically that an unexpected low-impedance conduction path has been established between the signal line and the system's ground reference (GND). This anomaly forces the voltage signal received by the control unit down to near zero potential, rendering the temperature feedback loop ineffective. The system cannot correctly interpret the actual refrigerant temperature, subsequently affecting air conditioning compressor start/stop logic and blower speed adjustment strategies, ultimately leading the control system into a protection or degraded operation mode.

Common Fault Symptoms

When the control unit determines and records this fault code, user experience within the vehicle cockpit will be intuitively affected. Here are the specific manifestations owners might perceive:

• Limited Air Conditioning System Functionality: Due to ineffective control logic, the cooling capacity of the air conditioning system may not be fully output, resulting in significantly reduced cabin cooling effect.
• Abnormal Temperature Control: There may be deviations between set temperature and actual outlet air temperature; the control system cannot maintain a preset constant temperature state.
• Fault Indicator Alarm: Vehicle service information or air conditioning system warning lights on the dashboard may light up, alerting the driver to electrical faults in the system.
• Partial Functions Unavailable: In certain driving modes, some auxiliary functions of the air conditioning system (such as automatic airflow adjustment) may be disabled, providing only manual or default modes.

Core Fault Cause Analysis

From a technical architecture perspective, the trigger mechanism for this fault code mainly involves hardware or connection reliability issues in three dimensions:

• Wiring and Connector Failures: This is the most common external factor. Insulation layer wear inside the harness causing wires to short directly to ground, or harness connectors (Connector) taking water ingress/corrosion causing short-circuit connections between contacts, will cause signal voltage to be pulled down to ground potential.
• Refrigerant Temperature Sensor 3 Failure: Electronic components aging or breakdown internally within the sensor body causing zero impedance between its internal signal output terminal and ground terminal, generating a permanent short circuit signal.
• Right Domain Controller Failure: As the control unit (ECU) receiving the signal, if its input port's analog-to-digital conversion circuit or protection circuit gets damaged, it may also incorrectly judge a wiring short to ground, or due to internal power management anomalies lead to false fault reporting.

Technical Monitoring and Trigger Logic

The control unit continuously monitors the electrical status of Refrigerant Temperature Sensor 3 in real-time dynamic monitoring, its core basis for fault determination is the degree of deviation from signal voltage thresholds. Specific technical monitoring logic follows:

• Monitoring Target: System continuously monitors signal line output voltage (Signal Voltage) coming from Refrigerant Temperature Sensor 3.
• Trigger Condition: Fault code is only activated when ignition switch is in ON position, after vehicle electrical system power supply becomes stable.
• Judgment Threshold: Control unit calculates and compares difference between real-time signal voltage value and preset reference values. Once detected sensor output voltage is below $0.1V$, and persists beyond specified monitoring window time, system determines line has serious short to ground phenomenon. This numerical range explicitly indicates signal wire has lost high-level characteristics, entered Grounded State.