DTC B0158 or B0168 Current

Diagnostic Instructions

DTC Descriptors

DTC B0158 03: Outside Air Temperature Sensor Circuit Voltage Below Threshold

DTC B0158 07: Outside Air Temperature Sensor Circuit Voltage Above Threshold

DTC B0168 03: Passenger Compartment Temperature Sensor Voltage Below Threshold

DTC B0168 07: Passenger Compartment Temperature Sensor Voltage Above Threshold

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Ambient Air Temperature Sensor Circuit	B0158 03	B0158 07	B0158 07	--
Inside Air Temperature Sensor Circuit	B0168 03	B0168 07	B0158 07	--

Circuit Description

The HVAC control module monitors the air temperature sensors with a low reference circuit and 5-volt signal circuit. The HVAC control module monitors the voltage drop across the sensor. When the ambient air temperatures are cold, the resistance of the sensor is high and the voltage signals are high. When the ambient air temperatures are hot, the resistance of the sensors is low and the voltage signals are low.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

Action Taken When the DTC Sets

B0158

B0168

Conditions for Clearing the DTC

Reference Information

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

Scan Tool Reference

Control Module References

Circuit/System Verification

Ignition ON, observe the appropriate scan tool Air Temp Sensor parameter. The reading should be between -35°C (-39°F) and 85°C (185°F) and change with air temperature changes.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the appropriate air temperature sensor.
2. Ignition OFF, test for less than 10 ohms between the following low reference circuit terminal and ground.

•	Outside air temperature sensor terminal A

•	Inside air temperature sensor terminal B

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.

3. Ignition ON, verify the appropriate scan tool Air Temp Sensor parameter is less than -35°C (-39°F).

⇒	If greater than the specified range, test the following signal circuit terminal for a short to ground. If the circuit tests normal, replace the HVAC control module.

•	Outside air temperature sensor terminal B

•	Inside air temperature sensor terminal A

4. Install a 3A fused jumper wire between the following signal circuit terminal and the low reference circuit terminal. Verify the scan tool Air Temp Sensor parameter is greater than 85°C (185°F).

•	Inside air temperature sensor terminal Aand B.

•	Ambient temperature sensor terminal B and A.

⇒	If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.

5. If all circuits test normal, test or replace the air temperature sensor.

Component Testing

Ignition OFF, remove the appropriate temperature sensor and perform a resistance test across the sensor terminals. Verify that the resistance readings correspond with those in the sensor resistance tables. If outside of the specified range, replace the appropriate sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.