HVAC System - Automatic

DTC B3933

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC B3933 03
- Evaporator Air Temperature Voltage High or above threshold Sensor

DTC B3933 07
- Evaporator Air Temperature Voltage Low or below threshold Sensor

Diagnostic Fault Information






Circuit Description

The HVAC control module monitors the evaporator temperature via the evaporator temperature sensor. When the air is cold, the sensor resistance and signal voltage are high. When the air is warm, the sensor resistance and signal voltage are low.

Conditions for Running the DTC

The ignition is turned ON.

Conditions for Setting the DTC

The HVAC control module detects the evaporator temperature sensor signal circuit is less than 0.443 volt or greater than 4.55 volts.

Action Taken When the DTC Sets

The air conditioning (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 50 fault-free ignition cycles.
* The DTC can be cleared with a scan tool.

Circuit/System Testing

1. Ignition OFF, disconnect the Evaporator Temperature Sensor harness connector at the Evaporator Temp Sensor.
2. Test for less than 1.0 ohm of resistance between the low reference circuit terminal 2 and ground.

• 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 Evaporator Temp Sensor Voltage parameter is greater than 4.55 volts.

• If less than the specified range, test the signal circuit terminal 1 for a short to ground. If the circuit tests normal, replace the HVAC control module.

4. Install a 3-amp fused jumper wire between the signal circuit terminal 1 and the low reference circuit terminal 2. Verify the scan tool Evaporator Air Temp 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, replace the Evaporator Temp Sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Evaporator Temperature Sensor Replacement
* Programming and RelearningProgramming and Relearning