For 1990-2009 cars

### DTC Descriptors

DTC B3933 03: Evaporator Temperature Sensor Voltage Below Threshold
DTC B3933 07: Evaporator Temperature Sensor Voltage Above Threshold

### Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle , prior to using this diagnostic procedure.

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Evaporator Temperature Sensor Signal | B0183 03 | B0183 03 | B0183 07 | --
Low Reference | -- | B0183 07 | B0183 07 | --

### 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 ON.

### Conditions for Setting the DTC

The HVAC control module detects the evaporator temperature sensor signal circuit is less than 0.09 volt (5 counts) or greater than 4.90 volts (250 counts).

### Action Taken When the DTC Sets

• | A warning will display on the Driver Information Centre (DIC) "SERVICE A/C SYSTEM"

• | The A/C compressor will be disabled.

### Conditions for Clearing the DTC

• | The condition for setting the DTC is no longer present.

• | The history DTC will clear after 50 fault-free ignition cycles.

• | The DTC can be cleared with a scan tool.

### Reference Information

#### Schematic Reference

HVAC Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References

### Circuit/System Verification

Ignition ON, using a scan tool, observe the evaporator temperature sensor parameter. The scan tool should display between 0.09 and 4.90 volts.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the evaporator air temperature sensor.
2. Ignition OFF, test for less than 10 ohms between the low reference circuit terminal A 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, test for 4.8-5.2 volts between the signal circuit terminal A and low reference circuit terminal B.

⇒ | 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 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 HVAC control module.

4. If all circuits test normal, test or replace the evaporator air temperature sensor.

### Repair Instructions

Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | HVAC Control Module Programming and Setup

• | Air Valve Actuator Control Module Harness Replacement