GM Service Manual Online
For 1990-2009 cars only

Object Number: 557011  Size: SF
HVAC Components
ECC Module and Temperature Sensors
Handling ESD Sensitive Parts Notice
ECC Module and Temperature Sensors

Circuit Description

The HVAC control module monitors the ambient light on the vehicle via light sensitive photodiode which is called a sunload sensor. The HVAC control module uses this information in order to compensate for the effect of the sun on the inside air temperature of the vehicle. When the sensor is in direct sunlight, the ambient light counts are low. When the sensor is shaded, the ambient light counts are high. The HVAC control module requests engagement of the A/C compressor clutch, and controls the door position of the air temperature actuator in order to maintain the selected air temperature on the HVAC control module.

Conditions for Running the DTC

The ignition is turned ON.

Conditions for Setting the DTC

The HVAC control module detects that the signal circuit is less than 5 Counts.

Action Taken When the DTC Sets

The HVAC control module uses a default sunload sensor value of approximately 0 Counts until the fault is cleared.

Conditions for Clearing the DTC

    • The DTC becomes history when the HVAC control module no longer detects a failure.
    • The history DTC clears after 50 fault-free ignition cycles.
    • The DTC can be cleared with a scan tool.

Diagnostic Aids

    • Insure sun load sensor is in place and secure. Insure no debris around sun load sensor this will give incorrect reading to HVAC control module.
    • If condition is not present refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

The number(s) below refer to the step number(s) 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

Value(s)

Yes

No

1

Did you perform the HVAC Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the Solar Sensor parameter in the Heating and Air Conditioning Data Display data list.

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

100-240 Counts

Go to Diagnostic Aids.

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 Solar Sensor parameter.

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

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

Does the scan tool indicate that the Solar Sensor parameter is greater 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 Special Tools 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 HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Special Tools 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

Replace the HVAC control module. Refer to Control Assembly 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