GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2006 🢒 Rendezvous - FWD 🢒 Accessories 🢒 Navigation Systems 🢒 DTC B3933

Circuit Description

The HVAC control module monitors the temperature of the refrigerant through the evaporator via a evaporator temperature sensor. When the refrigerant temperature is low the sensor resistance and the signal voltage are high. When the refrigerant temperature is high the sensor resistance and the signal voltage 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 too 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.

DTC Descriptors

This diagnostic procedure supports the following DTC:

B3933 Air Conditioning (A/C) Evaporator Temperature Sensor Circuit

Conditions for Running the DTC

The ignition is turned ON.

Conditions for Setting the DTC

The HVAC control module detects the signal circuit is less than 5 counts (0.09 volts).

Action Taken When the DTC Sets
    • The HVAC control module will store the trouble code in memory.
    • A default value will be used for the sensor data by the HVAC control module to allow the A/C system to operate.

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.

Diagnostic Aids

If the condition is not present, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Tests for the proper operation of the circuit in the high voltage range.

    2.

  2. Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.

Step

Action

Value(s)

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the Evaporator Temp parameter in the Heating, Ventilation and Air Conditioning data list.

Does the scan tool indicate that the Evaporator Temp parameter is within the specified range?

-50 to +143°C (-58 to +290°F)

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the evaporator temperature sensor
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Evaporator Temp parameter.

Does the scan tool indicate that the Evaporator Temp sensor parameter is equal to the specified value?

-43°C (-45°F)

Go to Step 5

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Connect a 3-amp fused jumper wire between the signal circuit of the evaporator temperature sensor and the low reference circuit of the evaporator temperature sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Evaporator Temp parameter.

Does the scan tool indicate that the EvaporatorTemp parameter is equal to the specified value?

144°C (291°F)

Go to Step 8

Go to Step 6

5

Test the signal circuit of the evaporator temperature sensor for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

6

Test the signal circuit of the evaporator temperature sensor for a short to voltage, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 7

7

Test the low reference circuit of the evaporator temperature sensor for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

8

Inspect for poor connections at the harness connector of the evaporator temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 10

9

Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 11

10

Replace the evaporator temperature sensor. Refer to Evaporator Temperature Sensor Replacement in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

--

Go to Step 12

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11

Replace the HVAC control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 12

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12
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK