GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2003 🢒 Park Avenue 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 DTC B1318 or B1328

Circuit Description

The following DTC's are for the left and right sunload sensors monitored by the instrument panel module (IPM):

    • B1318 - left sunload sensor
    • B1328 - right sunload sensor

The IPM monitors ambient light with the left and right sunload sensors. The sunload sensors are an infrared light sensitive photodiode. The IPM supplies 5 volts to the sunload sensors signal circuit and provides a low reference circuit. As the light shining upon the sensor gets brighter, the sensor conductance increases. The sensor signal decreases as the conductance increases. The IPM uses this information to compensate for the effect of the sun on the inside air temperature of the vehicle. The IPM converts the voltage values to count values where 1 V is approximately equal to 51 counts.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

The IPM detects the sunload sensor signal circuit is less than 0.09 volt (5 counts) or more than 4.90 volts (250 counts).

Action Taken When the DTC Sets

A default value of 240 counts will be substituted for the sensor data by the IPM.

    • Left sunload sensor
       - The Driver Solar displayed on the scan tool in the HVAC Sensors data list will be the default value.
       - The Left Solar Sensor displayed on the scan tool in the Open/Short data list will be the actual value.
    • Right sunload sensor
       - The Passenger Solar displayed on the scan tool in the HVAC Sensor data list will be the default value.
       - The Right Solar Sensor displayed on the scan tool in the Open/Short data list will be the actual value.

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 by using a scan tool.

Test Description

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

  1. The operating range of the sensor is between 0.09-4.90 volts. If the scan tool displays a value between 0-0.08 volt or 4.91-5.0 volts, then the sensor is performing outside of its designed limits.

    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.

    4.

  4. Tests the sensor signal circuit for a short to ground.

    5.

  5. Tests the sensor signal circuit for a short to voltage, a high resistance, or an open.

    6.

  6. Tests the low reference circuit for a high resistance or an open.

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?

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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 appropriate Solar Sensor parameter in the Heating and Air Conditioning Open/Short data list.

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

0.09-4.90 V

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

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

Does the scan tool indicate that the Solar Sensor parameter is more 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 solar sensor signal circuit 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 Solar Sensor parameter.

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

0.09 V

Go to Step 8

Go to Step 6

5

Test the appropriate solar sensor 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 appropriate solar sensor 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 appropriate 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 appropriate 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 the appropriate replacement procedure:

Did you complete the replacement?

--

Go to Step 12

--

11

Important: : Perform the recalibration procedure for the instrument panel integration module.

Replace the instrument panel integration module. Refer to Instrument Panel Module Replacement in Body Control System.

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