GM Service Manual Online
For 1990-2009 cars only

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 B0183 06: Solar Load Sensor 1 Circuit Short to Ground or Open

DTC B0188 06: Solar Load Sensor 2 Circuit Short to Ground or Open

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Left Sunload Sensor Signal

B0183 06

B0183 06

B0183 06

--

Right Sunload Sensor Signal

B0188 06

B0188 06

B0188 06

--

Low Reference

--

B0183 06, B0188 06

B0183 06, B0188 06

--

Circuit Description

The vehicle uses left and right sunload sensors that are integrated into one sensor assembly along with the ambient light sensor. Low reference and signal circuits enable the sensor to operate. The sensor signal varies between 0 and 5 volts. The HVAC control module converts the signal to a range between 0 and 255 counts. The sunload sensor provides the HVAC control module with a measurement of the amount of light shining on the vehicle. Bright or high intensity light causes the vehicles interior temperature to increase. The HVAC system compensates for the increased temperature by diverting additional cool air into the vehicle.

The following DTCs are for the left and right sunload sensors.

    • B0183 is for the left sunload sensor.
    • B0188 is for the right sunload sensor.

Conditions for Running the DTC

Ignition ON.

Conditions for Setting the DTC

The HVAC control module detects the signal circuit is less than 5 counts or greater than 250 counts.

Action Taken When the DTC Sets

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

Conditions for Clearing the DTC

    • The DTC will become history if the HVAC control module no longer detects the condition that set the DTC.
    • The history DTC will clear after 50 fault-free ignition cycles.

Reference Information

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, observe the appropriate scan tool Sunload Sensor parameter. The reading should be between 5 and 250 counts and change with sunlight changes.

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the sunload sensor.
  2. Test for less than 10 ohms between the ground circuit terminal C and ground.
  3. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, test for 4.8-5.2 volts between the ground circuit terminal C and the appropriate signal circuit terminal listed below:
  5. • Left solar load sensor circuit terminal A.
    • Right solar load sensor 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.
  6. If all circuits test normal, test or replace the sunload sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Headlamp Automatic Control Ambient Light Sensor Replacement
    •  Control Module References for HVAC control module replacement, setup, and programming