Diagnostic Instructions

DTC Descriptors

DTC B3933 13: Air Conditioning (A/C) Evaporator Temperature Sensor Circuit Low Voltage

DTC B3933 14: Air Conditioning (A/C) Evaporator Temperature Sensor Circuit High Voltage

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Evaporator Sensor Signal	B3933 14	B3933 14, B3933 13	B3933 13	--
Evaporator Low Reference Signal	--	1	--	--
1. A/C Compressor Will Not Engage

Circuit/System Description

The HVAC control module supplies the evaporator temperature sensor with a low reference circuit and 5-volt signal circuit. The HVAC control module determines the voltage drop across the sensor, which is proportional to temperature. When the refrigerant temperature is low the sensor resistance and voltage signal are high.

Conditions for Running the DTC

Ignition ON.

Conditions for Setting the DTC

The HVAC control module detects the evaporator air temperature sensor signal circuit is less than -40°C (-40°F) or more than 120°C (248°F) for more than 15 seconds.

Action Taken When the DTC Sets

The default value of 74°C (165.2°F) will be substituted for the evaporator.

Conditions for Clearing the DTC

Reference Information

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, observe the scan tool A/C Evaporator Temperature Sensor parameter. The reading should be between -35 and +98°C (-39 and +208°F) and change with evaporator air temperature changes.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the evaporator temperature sensor.
2. Ignition OFF, test for less than 1 ohm between the low reference circuit terminal B and ground.

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

3. Ignition ON, verify the scan tool Evaporator Air Temperature Sensor parameter is greater than 4.55 volts.

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

4. Install a 3A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool Evaporator Air Temperature Sensor Voltage parameter is less than 0.433 volt.

⇒	If greater 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 evaporator temperature sensor.

Component Testing

1. A thermometer can be used to test the sensor off the vehicle in warn and or cold water. Sensor Resistance Table for this test.
2. Test the appropriate temperature sensor by varying the sensor temperature in water while monitoring the sensor resistance.
3. Compare the readings with the Temperature VS Resistance table and verify that the resistance is within 5 percent of the specification.

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

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.