B133511 - B133511 Refrigerant Temperature Sensor 2 Short to Ground

B133511 Refrigerant Temperature Sensor 2 Short to Ground Technical Note

Fault Depth Definition

This DTC (B133511) indicates a specific monitoring circuit in the vehicle HVAC system has experienced an electrical anomaly, specifically pointing to a Short to Ground on the signal line of the Refrigerant Temperature Sensor 2. In the vehicle control architecture, such faults typically involve the input side of the Engine Control Unit or Body Control Module (Body Control Module). The control unit constructs a thermo-dynamic feedback loop inside and outside the cabin by acquiring analog signal voltages from sensors. This sensor is used to monitor the physical state of the refrigerant circulation system in real-time. When the signal line unexpectedly connects to ground potential, it causes significant deviation in the expected voltage reading at the control unit, triggering the fault code to protect the system from incorrect data-driven decision-making.

Common Fault Symptoms

Because the air conditioning control system relies on accurate temperature feedback for calculation of adjustment strategies, the following characteristics may manifest when this DTC is activated:

• Partial HVAC System Failure: The vehicle thermal management system may enter an automatic degradation mode and fail to maintain the set target temperature.
• Dashboard Warning Lights Ignite: The driver may observe relevant system fault indicator lights or Engine Malfunction Indicator Light (MIL) lit up on the instrument cluster.
• Abnormal Cooling Performance: In terms of driving experience, passengers may perceive insufficient air conditioning cooling output or a complete loss of temperature control capability.
• Limited System Adaptive Functions: The vehicle's automatic thermal management adjustment strategies may temporarily fail, leading to erratic compressor on/off logic.

Core Fault Cause Analysis

Based on the technical architecture, the root causes of this fault can be analyzed from three dimensions: hardware components, physical connections, and control unit logic:

1. Hardware Component Failure: Primarily points to insulation performance failure or component aging within the Refrigerant Temperature Sensor 2 itself, causing direct grounding at the signal output terminal.
2. Wiring or Connector Failure: The vehicle wiring harness may show signs of wear, corrosion, or physical crushing damage, creating a short circuit point between the signal line and the chassis ground; simultaneously, connector terminals may conduct to ground due to poor contact or intrusion of foreign objects.
3. Controller Internal Fault: Abnormality in input circuit logic operation units or power management modules inside the Right Domain Controller (Right Domain Controller) may lead to erroneous determination of sensor signal status.

Technical Monitoring and Trigger Logic

The control unit uses a real-time voltage threshold comparison algorithm to identify such short-to-ground faults, following strict electrical logic in its monitoring process:

• Monitoring Target: The system continuously monitors the output voltage value from the signal line of Refrigerant Temperature Sensor 2.
• Fault Judgment Numeric Range: When sensor output voltage is detected to be $< 0.1V$, the system will determine that there is a risk of signal line short-to-ground. This threshold is far below the normal sensor analog divider ratio, indicating the voltage has been pulled directly down to ground potential.
• Trigger Operating Conditions: The aforementioned monitoring and logic judgment are only valid when executed while the Ignition Switch is in ON Position and the Engine Control Unit enters active operation mode. Only then does the control unit activate the data acquisition channel to compare input signals against a pre-defined safe range; once short-circuit criteria are met for a duration exceeding the specified threshold, DTC B133511 is written.