Pinpoint Test G: B1B71
Climate Control System
Pinpoint Tests
Pinpoint Test G: B1B71
Refer to Wiring Diagram Set 55, Automatic Climate Control System for schematic and connector information. Diagrams By Number
Refer to Wiring Diagram Set 54, Manual Climate Control System for schematic and connector information. Diagrams By Number
Normal Operation
Under normal operation, the evaporator discharge air temperature sensor receives a ground from the HVAC module through circuit RH111 (GY/BU). A 5-volt reference voltage is supplied to the evaporator discharge air temperature sensor from the HVAC module through circuit VH406 (VT/BN).
- DTC B1B71:11 Evaporator Temperature Sensor: Circuit Short to Ground - The module senses excessive voltage drop on the sensor reference voltage circuit, indicating a short directly to ground.
- DTC B1B71:15 Evaporator Temperature Sensor: Circuit Short to Battery or Open - The module senses no voltage drop on the sensor reference voltage circuit, indicating a short directly to voltage or an open circuit.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Evaporator discharge air temperature sensor
- HVAC module
PINPOINT TEST G: B1B71
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G1 CHECK THE SENSOR RESISTANCE
- Ignition OFF.
- Disconnect: Evaporator Discharge Temperature Sensor C296.
- Measure the resistance between the evaporator discharge temperature sensor C296 terminals and compare to the table below.
- Is the resistance within the specified values for the temperatures?
Yes
GO to G2.
No
INSTALL a new evaporator discharge sensor. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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G2 CHECK THE SENSOR OUTPUT VOLTAGE
- Ignition ON.
- Press the AUTO button.
- Measure the voltage between evaporator discharge temperature sensor C296-1, circuit VH406 (VT/BN), harness side and C296-2, circuit RH111 (GY/BU), harness side.
- Is the voltage between 4.7 and 5.1 volts?
Yes
INSTALL a new evaporator discharge sensor. CLEAR the DTCs. REPEAT the self-test. If code returns, GO to G8.
No
If diagnosing DTC B1B71:15, GO to G3.
If diagnosing DTC B1B71:11, GO to G6.
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G3 CHECK CIRCUIT VH406 (VT/BN) FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: HVAC Module C228a.
- Ignition ON.
- Measure the voltage between ground and HVAC module C228a-6, circuit VH406 (VT/BN), harness side and ground.
- 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 G4.
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G4 CHECK CIRCUIT VH406 (VT/BN) FOR AN OPEN
- Ignition OFF.
- Measure the resistance between HVAC module C228a-6, circuit VH406 (VT/BN), harness side and evaporator discharge temperature sensor C296-1, circuit VH406 (VT/BN), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to G5.
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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G5 CHECK CIRCUIT RH111 (GY/BU) FOR AN OPEN
- Measure the resistance between HVAC module C228a-10, circuit RH111 (GY/BU), harness side and evaporator discharge temperature sensor C296-2, circuit RH111 (GY/BU), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to G8.
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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G6 CHECK CIRCUIT VH406 (VT/BN) FOR A SHORT TO CIRCUIT RH111 (GY/BU)
- Ignition OFF.
- Disconnect: HVAC Module C228a.
- Measure the resistance between evaporator discharge temperature sensor C296-1, circuit VH406 (VT/BN), harness side and C296-2, circuit RH111 (GY/BU), harness side.
- Is the resistance greater than 10,000 ohms?
Yes
GO to G7.
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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G7 CHECK CIRCUIT VH406 (VT/BN) FOR A SHORT TO GROUND
- Measure the resistance between HVAC module C228a-6, circuit VH406 (VT/BN), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to G8.
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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G8 CHECK THE MODULE CONNECTION
- Carry out the HVAC Module Cold Boot Process. HVAC Module Cold Boot Process
- Carry out the HVAC Module On-Demand Self Test. Alternate Diagnostic Methods - HVAC Module
- Operate the system.
- Does the concern return?
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.
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