Pinpoint Test G: B1B71
Climate Control System
Pinpoint Tests
Pinpoint Test G: B1B71
Normal Operation
Under normal operation, the evaporator discharge air temperature sensor receives a ground from the HVAC module through circuit RH107 (GN/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 Air Temperature Sensor C296.
- Measure the resistance between the evaporator discharge air 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 air temperature 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 air temperature sensor C296-1, circuit VH406 (VT/BN), harness side and C296-2, circuit RH107 (GN/BU), 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. 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/C2356a.
- Ignition ON.
- Measure the voltage between ground and HVAC module C228a/C2356a-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/C2356a-6, circuit VH406 (VT/BN), harness side and evaporator discharge air 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 RH107 (GN/BU) FOR AN OPEN
- Measure the resistance between HVAC module C228a/C2356a-10, circuit RH107 (GN/BU), harness side and evaporator discharge air temperature sensor C296-2, circuit RH107 (GN/BU), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to G8.
No
REPAIR circuit RH107 (GN/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 RH107 (GN/BU)
- Ignition OFF.
- Disconnect: HVAC Module C228a/C2356a.
- Measure the resistance between evaporator discharge temperature sensor C296-1, circuit VH406 (VT/BN), harness side and C296-2, circuit RH107 (GN/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 RH107 (GN/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/C2356a-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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