HVAC - Manual
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 Descriptors
DTC B3933 02
- A/C Evaporator Air Temperature Sensor Short to Ground
DTC B3933 05
- A/C Evaporator Temperature Sensor Circuit Short to Battery or Open
Diagnostic Fault Information
Circuit Description
The HVAC control module supplies the evaporator air 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 air temperature increases, the sensor resistance decreases and the voltage signal decreases. As the air temperature decreases, the sensor resistance increases and the voltage signal increases.
Conditions for Running the DTC
The ignition is turned ON.
Conditions for Setting the DTC
The HVAC control module detects the evaporator air temperature sensor signal circuit is less than -36°C (-38°F) or more than 215°C (419°F) for more than 15 seconds.
Action Taken When the DTC Sets
The A/C compressor will be disabled.
Conditions for Clearing the DTC
* The DTC will become history if the HVAC control module no longer detects a failure.
* The history DTC will clear after 100 fault-free ignition cycles have occurred.
Reference Information
Schematic Reference
HVAC Schematics HVAC - Manual
Connector End View Reference
Component Connector End Views Connector End Views By Name
Description and Operation
* Air Delivery Description and Operation Air Delivery
* Air Temperature Description and Operation Air Temperature
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 Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON
2. Verify the scan tool A/C Evaporator Temperature Sensor parameter is between-35°C (-39°F) and 85°C (185°F) and changes with evaporator air temperature changes.
• If not between -35°C (-39°F) and 85°C (185°F) or does not change
Refer to Circuit/System Testing
• If between -35°C (-39°F) and 85°C (185°F) changes
3. All OK
Circuit/System Testing
1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the evaporator air temperature sensor. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 5 ohms between the low reference circuit terminal B and ground.
• If 5 ohms or greater
1. Ignition OFF, disconnect the X3 harness connector at the HVAC control module.
2. Test for less than 2 ohms in the low reference circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the HVAC control module.
• If less than 5 ohms
3. Ignition ON
4. Verify the scan tool A/C Evaporator Temperature Sensor parameter is less than -35°C (-39°F).
• If -35°C (-39°F) or greater
1. Ignition OFF, disconnect the X3 harness connector at the HVAC control module.
2. Test for infinite resistance between the signal circuit terminal A and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the HVAC control module.
• If less than -35°C (-39°F)
5. Install a 3 A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B.
6. Verify the scan tool A/C Evaporator Temperature Sensor parameter is greater than 85°C (185°F).
• If 85°C (185°F) or less
1. Ignition OFF, disconnect the X3 harness connector at the HVAC control module, Ignition ON.
2. Test for less than 1 V between the signal circuit terminal A and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V
3. Test for less than 2 ohms in the signal circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the HVAC control module.
• If greater than 85°C (185°F)
7. Test or replace the evaporator air temperature sensor.
Component Testing
1. Ignition OFF, disconnect the harness connector at the evaporator temperature sensor.
2. Measure the resistance between terminal A and terminal B.
3. Verify the resistance is within 5 % of the specified readings contained in the Sensor Resistance Table Electrical Specifications.
• If not within 5 %
Replace the evaporator air temperature sensor
• If within 5 %
4. All OK.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Air Conditioning Refrigerant Temperature Sensor Replacement Service and Repair
* Control Module References Control Module References for HVAC control module replacement, programming, and setup