Pinpoint Test F: DTCs B1B71:11 and 15
Climate Control System
Pinpoint Tests
Pinpoint Test F: DTCs B1B71:11 and 15
Refer to Wiring Diagram Set 54, Manual Climate Control System for schematic and connector information. Diagrams By Number
Refer to Wiring Diagram Set 55, Automatic Climate Control System for schematic and connector information. Diagrams By Number
Normal Operation
Under normal operation, 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 temperature measurement is used by the HVAC module to turn the A/C compressor off before the evaporator temperatures are cold enough to freeze the condensation. This prevents ice blockage of airflow over the evaporator core.
- DTC B1B71:11 (Evaporator Temperature Sensor: Circuit Short to Ground) - The module senses lower than expected voltage on the sensor feedback circuit, indicating a short to ground.
- DTC B1B71:15 (Evaporator Temperature Sensor: Circuit Short to Battery or Open) - The module senses greater than expected voltage on the sensor feedback circuit, indicating a short to voltage or an open circuit or sensor.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Evaporator temperature sensor
- HVAC module
PINPOINT TEST F: DTCs B1B71:11 AND 15
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F1 CHECK THE EVAPORATOR TEMPERATURE SENSOR RESISTANCE
- Ignition OFF.
- Disconnect: Evaporator Temperature Sensor C296.
- Measure the resistance between the evaporator temperature sensor C296 terminals, component side and compare to the table below.
- Is the resistance within the specified values for the temperatures?
Yes
GO to F2.
No
INSTALL a new evaporator temperature sensor. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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F2 CHECK THE HVAC MODULE OUTPUT VOLTAGE
- Ignition ON.
- Press the POWER button.
- Measure the voltage between evaporator temperature sensor C296-2, circuit VH406 (VT/BN), harness side and C296-1, circuit RH111 (GY/BU), harness side.
- Is the voltage between 4.7 and 5.1 volts?
Yes
INSTALL a new evaporator temperature sensor. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation. If the DTC returns, GO to F8.
No
For DTC B1B71:15, GO to F3.
For DTC B1B71:11, GO to F6.
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F3 CHECK THE EVAPORATOR TEMPERATURE SENSOR FEEDBACK CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: HVAC Module C228.
- Ignition ON.
- Measure the voltage between ground and HVAC module C228-19, circuit VH406 (VT/BN), harness side.
- Is any voltage present?
Yes
REPAIR circuit VH406 (VT/BN) for a short to voltage. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
No
GO to F4.
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F4 CHECK THE EVAPORATOR TEMPERATURE SENSOR FEEDBACK CIRCUIT FOR AN OPEN
- Ignition OFF.
- Measure the resistance between HVAC module C228-19, circuit VH406 (VT/BN), harness side and evaporator temperature sensor C296-2, circuit VH406 (VT/BN), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to F5.
No
REPAIR circuit VH406 (VT/BN) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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F5 CHECK THE SIGNAL RETURN CIRCUIT FOR AN OPEN
- Measure the resistance between HVAC module C228-23, circuit RH111 (GY/BU), harness side and evaporator temperature sensor C296-1, circuit RH111 (GY/BU), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to F8.
No
REPAIR circuit RH111 (GY/BU) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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F6 CHECK THE EVAPORATOR TEMPERATURE SENSOR FEEDBACK CIRCUIT FOR A SHORT TO THE SIGNAL RETURN CIRCUIT
- Ignition OFF.
- Disconnect: HVAC Module C228.
- Measure the resistance between evaporator temperature sensor C296-2, circuit VH406 (VT/BN), harness side and C296-1, circuit RH111 (GY/BU), harness side.
- Is the resistance greater than 10,000 ohms?
Yes
GO to F7.
No
REPAIR circuit VH406 (VT/BN) for a short to circuit RH111 (GY/BU). CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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F7 CHECK THE EVAPORATOR TEMPERATURE SENSOR FEEDBACK CIRCUIT FOR A SHORT TO GROUND
- Measure the resistance between ground and HVAC module C228-19, circuit VH406 (VT/BN), harness side.
- Is the resistance greater than 10,000 ohms?
Yes
GO to F8.
No
REPAIR circuit VH406 (VT/BN) for a short to ground. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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F8 CHECK THE HVAC MODULE CONNECTION
- Inspect the HVAC module connectors for:
- corrosion.
- pushed-out terminals.
- damaged terminals.
- Connect and correctly seat all the HVAC module connectors.
- Clear the DTCs.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new HVAC module. REFER to Climate Control Heating Ventilation Air Conditioning (HVAC) Module. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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