Pinpoint Test G: DTCs B1B71:11 and 15

Climate Control System

Pinpoint Test G: 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 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.

- DTC B1B71:11 (Evaporator Discharge Air Temperature Sensor: Circuit Short to Ground)- The module senses excessive voltage drop on the sensor feedback circuit, indicating a short directly to ground.

- DTC B1B71:15 (Evaporator Discharge Air Temperature Sensor: Circuit Short to Battery or Open)- The module senses no voltage drop on the sensor feedback 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 : DTCs B1B71:11 AND 15

G1 CHECK THE SENSOR RESISTANCE

- Ignition OFF.

- Disconnect: Evaporator Discharge Air Temperature Sensor C296.

- Measure the resistance between the evaporator 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 an evaporator discharge air temperature sensor. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.

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
GO to G8.

No

For DTC B1B71:15, GO to G3.

For DTC B1B71:11, GO to G6.

G3 CHECK CIRCUIT VH406 (VT/BN) 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:
- (EMTC (Electronic Manual Temperature Control) systems) HVAC module- EMTC (Electronic Manual Temperature Control) C2357-8, circuit VH406 (VT/BN), harness side.

- (DATC (Dual Automatic Temperature Control) systems) HVAC module- DATC (Dual Automatic Temperature Control) C228A-8, 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 G4.

G4 CHECK CIRCUIT VH406 (VT/BN) FOR AN OPEN

- Ignition OFF.

- Measure the resistance between:
- (EMTC (Electronic Manual Temperature Control) systems) HVAC module- EMTC (Electronic Manual Temperature Control) C2357-8, circuit VH406 (VT/BN), harness side and evaporator discharge air temperature sensor C296-1, circuit VH406 (VT/BN), harness side.

- (DATC (Dual Automatic Temperature Control) systems) HVAC module- DATC (Dual Automatic Temperature Control) C228A-8, 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.

G5 CHECK CIRCUIT RH107 (GN/BU) FOR AN OPEN

- Measure the resistance between:
- (EMTC (Electronic Manual Temperature Control) systems) HVAC module- EMTC (Electronic Manual Temperature Control) C2357-4, circuit RH107 (GN/BU), harness side and evaporator discharge air temperature sensor C296-2, circuit RH107 (GN/BU), harness side.

- (DATC (Dual Automatic Temperature Control) systems) HVAC module- DATC (Dual Automatic Temperature Control) C228A-4, 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.

G6 CHECK CIRCUIT VH406 (VT/BN) FOR A SHORT TO CIRCUIT RH107 (GN/BU)

- 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 C296-1, 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.

G7 CHECK CIRCUIT VH406 (VT/BN) FOR A SHORT TO GROUND

- Measure the resistance between ground and:
- (EMTC (Electronic Manual Temperature Control) systems) HVAC module- EMTC (Electronic Manual Temperature Control) C2357-8, circuit VH406 (VT/BN), harness side.

- (DATC (Dual Automatic Temperature Control) systems) HVAC module- DATC (Dual Automatic Temperature Control) C228A-8, circuit VH406 (VT/BN), harness side.






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.

G8 CHECK THE MODULE CONNECTION

- Inspect the 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. 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.