GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2007 🢒 STS 🢒 Steering 🢒 Steering Wheel and Column 🢒 DTC B0183 or B0188

Circuit Description

The sunload sensor is a 2-wire photo diode. The vehicle uses left and right sunload sensors. The 2 sensors are integrated into the sunload sensor assembly along with the ambient light sensor. Low reference and signal circuits enable the sensor to operate. As the sunload increases, the sensor signal decreases. The sensor operates within an intensity range between completely dark and bright. The sensor signal varies between 0-5 volts. The HVAC control module converts the signal to a range between 0-255 counts. The sunload sensor provides the HVAC control module a measurement of the amount of light shining on the vehicle. Bright, or high intensity, light causes the vehicle's inside temperature to increase. The HVAC system compensates for the increased temperature by diverting additional cool air into the vehicle.

    • Solar Load Sensor 1 Circuit refers to the left sunload sensor
    • Solar Load Sensor 2 Circuit refers to the right sunload sensor

DTC Descriptors

This diagnostic procedure supports the following DTCs:

    • DTC B0183 Solar Load Sensor 1 Circuit
    • DTC B0188 Solar Load Sensor 2 Circuit

This vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to DTC Symptom Description .

DTC Symptom

DTC Symptom Descriptor

00

Out of Range Condition

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 0.09 volt (5 counts) or more than 4.90 volts (250 counts).

Action Taken When the DTC Sets
    • If the DTC is set the system will act as if no sunload condition exists.
    • The driver information center (DIC) will display SERVICE A/C SYSTEM.

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.

Test Description

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

  1. This step tests for the proper operation of the circuit in the high voltage range.

    2.

  2. This step 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

Connector End View Reference: HVAC Connector End Views

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 Driver or Passenger Solar Sensor parameter in the Climate Control Panel Open/Short Data list.

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

0.09-4.90 V

Go to Testing for Intermittent Conditions and Poor Connections

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 Driver or Passenger Solar Sensor parameter in the Climate Control Panel Open/Short Data list.

Does the scan tool indicate that the Solar Sensor parameters are greater than the specified value?

4.90 V

Go to Step 4

Go to Step 5

4

  1. Turn OFF the ignition.
  2. Connect a 3-amp fused jumper wire between the driver or passenger signal circuit of the sunload sensor assembly and the low reference circuit of the sunload sensor assembly.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Driver or Passenger Solar Sensor parameter in the Climate Control Panel Open/Short Data list.

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

0.09 V

Go to Step 9

Go to Step 6

5

Test the driver or passenger 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 13

Go to Step 10

6

Test the driver or passenger 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 13

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 13

Go to Step 8

8

Test the following signal circuits for a short to voltage:

    • Evaporator temperature sensor
    • Ambient air temperature sensor
    • Inside air temperature sensor
    • Left or Right sunload sensor
    • Ambient light sensor

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 13

Go to Step 10

9

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 13

Go to Step 11

10

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 13

Go to Step 12

11

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

Did you complete the replacement?

--

Go to Step 13

--

12

Replace the HVAC control module. Refer to Control Module References for replacement, setup and programming.

Did you complete the replacement?

--

Go to Step 13

--

13
  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