Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | 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 13: Evaporator Air Temperature Voltage High SensorDTC B3933 14: Evaporator Air Temperature Voltage Low Sensor
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Evaporator Sensor Signal | B3933 13 | B3933 14 | B3933 14 | -- |
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. When the refrigerant temperature is high the sensor resistance and voltage signal are low. The sensor works in conjunction with a switch to meter the flow of refrigerant therefore preventing the freezing of moisture that condenses on the evaporator. An evaporator with little refrigerant will starve causing insufficient cooling. An evaporator flooded with refrigerant will also cause poor cooling when there is too much liquid refrigerant that cannot vaporize quickly.
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. |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the evaporator temperature sensor harness connector at the evaporator temperature sensor.
- Ignition OFF, test for less than 1 ohm between the low reference circuit terminal B and ground of the evaporator temperature sensor.
- Ignition ON, verify the evaporator air temperature sensor parameter is greater than 4.55 volts.
- Install a 3A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B of the sensor. Verify the evaporator air temperature sensor voltage parameter is less than 0.433 volt.
- If all circuits test normal, test or replace the evaporator temperature sensor.
| ⇒ | 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. |
| ⇒ | 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. |
| ⇒ | 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. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for HVAC control module replacement, setup and programming |
