B0188

DTC B0183 or B0188

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions)provides an overview of each diagnostic category.



DTC Descriptors
DTC B0183 05
- Solar Load Sensor 1 Circuit Short to Short to Battery or Open

DTC B0183 02
- Solar Load Sensor 1 Circuit Short to Ground

DTC B0188 05
- Solar Load Sensor 2 Circuit Short to Short to Battery or Open

DTC B0188 02
- Solar Load Sensor 2 Circuit Short to Ground




Diagnostic Fault Information






Circuit Description

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.


The left and right sunload sensors provide the HVAC control module with inputs as to the amount heat load the sun is placing on the interior of the vehicle. The sunload sensors are photodiodes that are sensitive to light intensity. The body control module (BCM) applies 5 volts to internal input resistors that are connected to the left and right signal circuits of the sunload sensor assembly. The BCM provides ground to the sensors through the low reference circuit. The BCM monitors the voltage drops across the sunload sensors and converts the voltage values to count values where 1 volt is approximately equal to 51 counts. As the light intensity increases, the sunload sensors allow more current to travel through the circuits and the signal voltages decrease. As the light intensity decreases, the sunload sensor allow less current to travel through the circuits and the signal voltages increase. The BCM transmits the data to the HVAC control module over the GM LAN data circuit.


Conditions for Running the DTC

The ignition is ON.


Conditions for Setting the DTC

The BCM determines that the value of the sunload sensor signal is less than 5 counts (1 volt) or greater than 250 counts (5 volts).


Action Taken When the DTC Sets

The action taken will be for the BCM to revert to a calibrated default value.


Conditions for Clearing the DTC

* The DTC will become history if the BCM no longer detects a failure.
* The history DTC will clear after 100 fault-free ignition cycles.
* The DTC can be cleared with a scan tool.



Reference Information
Schematic Reference

HVAC Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Component Connector End Views)
Description and Operation

* Air Temperature Description and Operation (Air Temperature Description and Operation)
* Air Delivery Description and Operation (Air Delivery Description and Operation)

Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Programming and Relearning (Programming and Relearning)for Scan Tool Information


Circuit/System Testing

1. Ignition OFF, disconnect the sunload sensor harness connector at the Sunload Sensor.
2. Test for less than 1.0 ohm of resistance between the ground circuit terminal C and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify the appropriate Sunload Sensor voltage parameter is greater than 4.9 volts or 250 counts.

• If less than the specified range test the appropriate signal circuit terminal A or B for a short to ground. If the circuit tests normal, replace the HVAC control module.

4. Install a 3-amp fused jumper wire between the appropriate signal circuit terminal A or B and the ground circuit terminal C. Verify the scan tool Sunload Count parameter is less than the 0.1 volt or 5 counts.

• If greater than the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.

5. If all circuits test normal, replace the Sunload Sensor.



Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Ambient Light Sensor Replacement (Service and Repair)
* Programming and Relearning (Programming and Relearning)for HVAC control module replacement, setup, and programming