GM Service Manual Online
For 1990-2009 cars only

Circuit Description

    • B1318 is for the left sunload sensor.
    • B1328 is for the right sunload sensor.

The sunload sensor is a 2 wire photo diode. The vehicle uses left and right sunload sensors. Low reference and signal circuits enable the sensors to operate. As the light shining upon the sensor gets brighter, 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 (IPM) converts the signal to a range between 0-255 counts. The sunload sensor provides the IPM a measurement of the amount of light shining on the vehicle. Bright, or high intensity, light causes the vehicles inside temperature to increase. The HVAC system compensates for the increased temperature by diverting additional cool air into the vehicle.

Conditions for Running the DTC

The ignition is turned ON.

Conditions for Setting the DTC

The IPM detects the signal circuit is less than 5 counts (0.09 V) or greater than 250 counts (4.90 V).

Action Taken When the DTC Sets

A default value will be used for the sensor data by the IPM. The scan tool displays the default Solar value in the Instrument Panel Module HVAC Sensors data list. The scan tool displays the actual Solar Sensor value in the Instrument Panel Module Open/Short data list.

Conditions for Clearing the DTC

    • The DTC will become history if the IPM 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. 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 HVAC Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Automatic

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the Left or Right Solar Sensor parameter in the Instrument Panel Module, Open/Short Data list.

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

5-250 counts

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the left or right sunload sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Left or Right Solar Sensor parameter in the Instrument Panel Module, Open/Short Data list.

Does the scan tool indicate that the Solar 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 signal circuit of the sunload sensor and the low reference circuit of the left sunload sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Left or Right Solar Sensor parameter in the Instrument Panel Module, Open/Short Data list.

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

5 counts

Go to Step 8

Go to Step 6

5

Test the signal circuit of the sunload 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 sunload 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 sunload 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 sunload 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 IPM. 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 sunload sensor. Refer to Sun Load Sensor Replacement .

Did you complete the replacement?

--

Go to Step 12

--

11

Important:  Perform the recalibration procedure for the IPM.

Replace the IPM. Refer to HVAC Control Module Replacement .

Did you complete the replacement?

--

Go to Step 12

--

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