PINPOINT TEST F : DTCs B1B71:11 OR 15: Notes
Diagnostic Overview
Diagnostics in this article assume a certain skill level and knowledge of Ford-specific diagnostic practices. Refer to Diagnostic Methods in Service Information for information about these practices.
Refer to Automatic Climate Control System , for schematic and connector information.
Normal Operation and Fault Conditions
The evaporator temperature sensor receives a ground from the HVAC module. The sensor varies its resistance with the temperature. As the temperature rises, the resistance falls. As the temperature falls, the resistance rises. The HVAC module measures this resistance to determine the temperature at the sensor.
The evaporator temperature sensor is used for A/C compressor cycling. An accurate evaporator temperature is critical to prevent evaporator icing. The HVAC module uses the temperature measurement to turn off the A/C compressor before the evaporator temperatures are cold enough to freeze the condensation. This prevents ice blockage of airflow over the evaporator core.
DTC Fault Trigger Conditions
| DTC | Description | Fault Trigger Conditions |
|---|---|---|
| B1B71:11 | Evaporator Temperature Sensor: Circuit Short to Ground | This CMDTC and on demand DTC sets when the HVAC module senses lower than expected voltage on the sensor feedback circuit, indicating a short to ground. |
| B1B71:15 | Evaporator Temperature Sensor: Circuit Short to Battery or Open | This CMDTC and on demand DTC sets when the HVAC module senses greater than expected voltage on the sensor feedback circuit, indicating a short to voltage or an open circuit or sensor. |
Possible Sources
- Wiring, terminals or connectors
- Evaporator temperature sensor
- HVAC module
Visual Inspection and Diagnostic Pre-checks
- Inspect loose or corroded HVAC module and evaporator temperature sensor connections.