Volt

DTC B046A

The HVAC control module supplies the temperature sensor with a low reference circuit and 5 V signal circuit. The HVAC control module determines the voltage drop across the sensor, which is proportional to temperature. As the temperature increases, the sensor resistance decreases and the voltage signal decreases. As the temperature decreases, the sensor resistance increases and the voltage signal increases.

The ignition is turned ON.

The HVAC control module detects the temperature sensor signal circuit is less than -38°F or more than 185°F for more than 15 seconds.

A default value is used when the DTC is set.

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Vehicle OFF and all vehicle systems OFF, disconnect the harness connector at the B135 coolant heater temperature sensor. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 Ω between the low reference circuit terminal 2 and ground.

⇒	If 10 Ω or greater

2.1.	Vehicle OFF, disconnect the harness connector at the K33 HVAC control module.

2.2.	Test for less than 2 Ω in the low reference circuit end to end.

⇒	If 2 Ω or greater, repair the open/high resistance in the circuit.

⇒	If less than 2 Ω, replace the K33 HVAC control module.

⇓	If less than 10 Ω

3. Vehicle in Service Mode.
4. Verify the scan tool Heater Core Coolant Temperature Sensor parameter is less than -35°F.

⇒	If -35°F or greater

4.1.	Vehicle OFF, disconnect the harness connector at the K33 HVAC control module.

4.2.	Test for infinite resistance between the signal circuit terminal 1 and ground.

⇒	If less than infinite resistance, repair the short to ground on the circuit.

⇒	If infinite resistance, replace the K33 HVAC control module.

⇓	If less than -35°F

5. Install a 3 A fused jumper wire between the signal circuit terminal 1 and the low reference circuit terminal 2.
6. Verify the scan tool Heater Core Coolant Temperature Sensor parameter is greater than 240°F.

⇒	If 240°F or less

6.1.	Vehicle OFF, disconnect the harness connector at the K33 HVAC control module, vehicle in Service Mode.

6.2.	Test for less than 1 V between the signal circuit and ground.

⇒	If 1 V or greater, repair the short to voltage on the circuit.

⇓	If less than 1 V

6.3.	Vehicle OFF.

6.4.	Test for less than 2 Ω in the signal circuit end to end.

⇒	If 2 Ω or greater, repair the open/high resistance in the circuit.

⇒	If less than 2 Ω, replace the K33 HVAC control module.

⇓	If greater than 240°F

7. Test or replace the B135 coolant heater temperature sensor.

1. Test the temperature sensor by varying the sensor temperature while monitoring the sensor resistance.
2. Compare the readings with the Temperature Versus Resistance and verify that the resistance is within 5 percent of the specification.

⇒	If not within the specified range, replace the sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.