Pinpoint Test F: DTCs B1B71:11 and 15
Climate Control System
Pinpoint Test F: DTCs B1B71:11 and 15
Refer to Wiring Diagram Set 54, Manual Climate Control System for schematic and connector information Electrical Diagrams.
Refer to Wiring Diagram Set 55, Automatic Climate Control System for schematic and connector information Electrical Diagrams.
Normal Operation
The evaporator discharge air 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 discharge air 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 B1B71:11 (Evaporator Temperature Sensor: Circuit Short to Ground)- The HVAC 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 HVAC 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 discharge air temperature sensor
- HVAC module
PINPOINT TEST F : DTCs B1B71:11 AND 15
F1 CHECK THE SENSOR RESISTANCE
- Ignition OFF.
- Disconnect: Evaporator Temperature Sensor C296.
- Carry out the Evaporator Discharge Air Temperature Sensor component test. Component Tests
Does the evaporator discharge air temperature sensor test OK?
Yes
GO to F2.
No
INSTALL a new evaporator discharge air temperature sensor. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
F2 CHECK THE HVAC MODULE OUTPUT VOLTAGE
- Ignition ON.
- Press the POWER button on the HVAC controls.
- Measure the voltage between evaporator discharge air temperature sensor C296-2, circuit (LG/BK), harness side and C296-1, circuit (BK), harness side.
Is the voltage between 4.7 and 5.1 volts?
Yes
INSTALL a new evaporator discharge air 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 B1B71:11, GO to F6.
For DTC B1B71:15, GO to F3.
F3 CHECK THE EVAPORATOR TEMPERATURE SENSOR FEEDBACK CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: HVAC Module- Electronic Manual Temperature Control (EMTC) C2357.
- Disconnect: HVAC Module- Dual Automatic Temperature Control (DATC) C228A.
- Ignition ON.
- Measure the voltage between ground and:
- For EMTC (Electronic Manual Temperature Control) systems, HVAC Module- EMTC (Electronic Manual Temperature Control) C2357-19, circuit VH406 (VT/BN), harness side.
- For DATC (Dual Automatic Temperature Control) systems, HVAC module- DATC (Dual Automatic Temperature Control) C228A-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.
F4 CHECK THE EVAPORATOR TEMPERATURE SENSOR FEEDBACK CIRCUIT FOR AN OPEN
- Ignition OFF.
- Measure the resistance between:
- For EMTC (Electronic Manual Temperature Control) systems, HVAC module- EMTC (Electronic Manual Temperature Control) C2357-19, circuit VH406 (VT/BN), harness side and evaporator discharge air temperature sensor C296-2, circuit (LG/BK), harness side.
- For DATC (Dual Automatic Temperature Control) systems, HVAC module- DATC (Dual Automatic Temperature Control) C228A-19, circuit VH406 (VT/BN), harness side and evaporator discharge air temperature sensor C296-2, circuit (LG/BK), harness side.
Is the resistance less than 5 ohms?
Yes
GO to F5.
No
REPAIR circuit VH406 (VT/BN)/(LG/BK) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
F5 CHECK THE SIGNAL RETURN CIRCUIT FOR AN OPEN
- Measure the resistance between:
- For EMTC (Electronic Manual Temperature Control) systems, HVAC module- EMTC (Electronic Manual Temperature Control) C2357-23, circuit RH111 (GY/BU), harness side and evaporator discharge air temperature sensor C296-1, circuit (BK), harness side.
- For DATC (Dual Automatic Temperature Control) systems, HVAC module- DATC (Dual Automatic Temperature Control) C228A-23, circuit RH111 (GY/BU), harness side and evaporator discharge air temperature sensor C296-1, circuit (BK), harness side.
Is the resistance less than 5 ohms?
Yes
GO to F8.
No
REPAIR circuit RH111 (GY/BU)/(BK) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
F6 CHECK THE EVAPORATOR TEMPERATURE SENSOR FEEDBACK CIRCUIT FOR A SHORT TO THE SIGNAL RETURN CIRCUIT
- Ignition OFF.
- Disconnect: HVAC Module- EMTC (Electronic Manual Temperature Control) C2357.
- Disconnect: HVAC Module- DATC (Dual Automatic Temperature Control) C228A.
- Measure the resistance between evaporator discharge air temperature sensor C296-2, circuit (LG/BK), harness side and C296-1, circuit (BK), harness side.
Is the resistance greater than 10,000 ohms?
Yes
GO to F7.
No
REPAIR circuit VH406 (VT/BN)/(LG/BK) for a short to circuit RH111 (GY/BU)/(BK). CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
F7 CHECK THE EVAPORATOR TEMPERATURE SENSOR FEEDBACK CIRCUIT FOR A SHORT TO GROUND
- Measure the resistance between ground and:
- For EMTC (Electronic Manual Temperature Control) systems, HVAC Module- EMTC (Electronic Manual Temperature Control) C2357-19, circuit VH406 (VT/BN), harness side.
- For DATC (Dual Automatic Temperature Control) systems, HVAC module- DATC (Dual Automatic Temperature Control) C228A-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)/(LG/BK) for a short to ground. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
F8 CHECK THE HVAC MODULE CONNECTION
- Inspect the HVAC module component and harness side connectors for:
- corrosion
- damaged pins
- pushed-out terminals
- Connect and correctly seat all the HVAC module connectors.
- Clear the DTCs.
- Enter the following diagnostic mode on the scan tool: Self-Test- HVAC Module.
- Operate the system and verify the concern is still present.
Is the concern still present?
Yes
INSTALL a new 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.