B3933
DTC B3933
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
DTC Descriptor
DTC B3933 02
- Air Conditioning Evaporator Temperature Sensor Circuit Short to Ground
DTC B3933 05
- Air Conditioning Evaporator Temperature Sensor Circuit High Voltage/Open
Diagnostic Fault Information
Circuit/System Description
The A/C evaporator temperature sensor is a 2-wire negative temperature co-efficient thermistor. A signal and low reference circuit enables the sensor to operate. As the air temperature surrounding the sensor increases, the sensor resistance decreases. The sensor signal voltage decreases as the resistance decreases. The sensor operates within a temperature range between -40 to +85°C (-40 to +185°F). The sensor signal varies between 0-5 V. The HVAC control module converts the signal to a range between 0-255 counts. As the air temperature increases the count value will decrease. If the HVAC control module detects a malfunctioning sensor, then the control module software will use a default air temperature value. The default action ensures that the HVAC system can adjust the inside air temperature near the desired temperature until the condition is corrected.
Conditions for Running the DTC
* Ignition ON.
* The HVAC control module is ON.
Conditions for Setting the DTC
The HVAC control module detects the sensor signal out of range. The signal voltage is less than 0.1 V or greater than 4.9 V for more than 50 ms.
Action Taken When the DTC Sets
The system operates using a default value.
Conditions for Clearing the DTC
The sensor signal is within specified range between 0.1-4.9 V.
Reference Information
Schematic Reference
HVAC Schematics ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Manual HVAC Description and Operation (HVAC - Manual)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
Scan Tool Reference
Control Module References (Programming and Relearning) 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 to +98°C (-39 to +208°F) and change with evaporator temperature changes.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the B39 A/C Evaporator Temperature Sensor.
2. Test for less than 5 ohm between the B39 A/C Evaporator Temperature Sensor low reference circuit terminal B and ground.
• If greater than the specified value, test the low reference circuit for an open/high resistance.
3. Ignition ON, test for 4.8-5.2 V between the B39 A/C Evaporator Temperature Sensor signal circuit terminal A and ground.
• If less than the specified range, test the signal circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the K33 HVAC Control Module.
• If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K33 HVAC Control Module.
4. If all circuits test normal, replace the B39 A/C Evaporator Temperature Sensor and verify the DTC does not reset.
• If the DTC resets, replace the K33 HVAC Control Module.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Evaporator Air Temperature Sensor Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for HVAC control module replacement, setup, and programming