GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2005 🢒 XLR 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 DTC B0184 or B0189

Circuit Description

The HVAC control module monitors the ambient light on the left and right side of the vehicle through a light sensitive photodiode called a sunload sensor assembly. The HVAC control module uses this information to compensate for the effect of the sun on the inside air temperature of the vehicle. When the sensor is in direct sunlight, the signal voltage is low. When the sensor is shaded, the signal voltage is high. The HVAC control module requests A/C compressor clutch engagement and controls the air temperature actuator door positions in order to maintain the selected air temperature on the HVAC control module.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

    • DTC B0184 Solar Load Sensor Left
    • DTC B0189 Solar Load Sensor Right

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) or greater than 250 counts (4.90 volts).

Action Taken When the DTC Sets

The HVAC control module uses a default sunload sensor value for further automatic control calculations. The default values are not displayed on the scan tool.

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 condition not present refer to Testing for Intermittent Conditions and Poor Connections .

Test Description

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

  1. Verifies that the temperature displayed is not within the calibrated range.

    2.

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

    3.

  3. 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

Values

Yes

No

Schematic Reference: HVAC Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the appropriate Sunload Sensor parameter in the HVAC Systems Automatic data list.

Does the scan tool indicate that the appropriate Sunload Sensor parameter is with in the specified range?

5-250 Counts

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the sunload sensor assembly.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the appropriate Sunload Sensor parameter.

Does the scan tool indicate that the appropriate Sunload Sensor parameter is greater than the specified value?

250 Counts

Go to Step 4

Go to Step 5

4

  1. Turn OFF the ignition.
  2. Connect a 3-amp fused jumper wire between the appropriate signal circuit of the sunload sensor assembly and the low reference circuit of the sunload sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the appropriate Sunload Sensor parameter.

Does the scan tool indicate that the appropriate Sunload Sensor parameter is less than the specified value?

5 Counts

Go to Step 8

Go to Step 6

5

Test the appropriate signal circuit of the sunload sensor assembly for a short to ground. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

6

Test the appropriate signal circuit of the sunload sensor assembly for a short to voltage, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 7

7

Test the low reference circuit of the sunload sensor assembly for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs .

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 sunload sensor assembly. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

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 .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 11

10

Replace the sunload sensor assembly. Refer to Sun Load Sensor Replacement .

Did you complete the replacement?

--

Go to Step 12

--

11

Replace the HVAC control module. Refer to Control Module References 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