Circuit Description
The HVAC control module determines the ambient light conditions either Daylight or Low Light based on the voltage from the ambient light sensor. The HVAC control module provides the ambient light sensor with a low reference circuit and a ambient light sensor signal circuit. The HVAC control module then sends out a class 2 message to the body control module (BCM) indicating the outside light condition base on the signal from the ambient light sensor. When the ambient light sensor detects Low Light or Daylight conditions, a varying voltage is applied to the HVAC control module through the ambient light sensor signal.
Conditions for Running the DTC
This test is run every 250 milliseconds.
Conditions for Setting the DTC
The twilight sensor voltage is less than 0.09 V or greater than 4.75 V on 3 consecutive tests.
Action Taken When the DTC Sets
Twilight status set to Low Light.
Conditions for Clearing the MIL/DTC
The HVAC control module does not detect a voltage that is less than or greater than the predetermined value during the diagnostic self test.
Diagnostic Aids
| • | The following may cause an intermittent: |
| - | Bent terminal |
| - | Backed out terminal |
| - | Damaged terminal |
| - | Poor terminal tension |
| - | Chafed wire |
| - | Broken wire inside the insulation |
| • | When diagnosing for an intermittent short or an open, manipulate the wire harness while watching the test equipment for changes. |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics Connector End View Reference: Master Electrical Component List | ||||
1 | Did you perform the Lighting System Diagnostic System Check? | -- | Go to Step 2 | |
2 |
Does the scan tool indicate that the Photocell parameter is within the specified range? | 50-250 Counts | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 |
3 |
Does the scan tool indicate that the Ambient Light Sensor parameter is less than the specified value? | 50 Counts | Go to Step 4 | Go to Step 8 |
4 |
Does the scan tool indicate that the Ambient Light Sensor parameter is greater than 60 counts? | Go to Step 5 | Go to Step 6 | |
5 | Test the low reference circuit of the sunload sensor for a short to battery positive voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 8 |
6 | Test the low reference circuit of the sunload sensor for a short to ground, 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 13 | Go to Step 7 |
7 | Test the ambient light sensor signal circuit of the sunload sensor for a short to ground, 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 13 | Go to Step 10 |
8 | Test the ambient light sensor signal circuit of the sunload sensor for a short to battery positive voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 9 |
9 | 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 13 | Go to Step 11 |
10 | Inspect for poor connections at the harness connector of the HVAC control module. 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 13 | Go to Step 12 |
11 | Replace the sunload sensor. Refer to Sunload and Twilight Sentinel Sensor Replacement in Instrument Panel, Gages and Console. Did you complete the replacement? | -- | Go to Step 13 | -- |
12 |
Important: Perform the setup procedure for the HVAC control module. Replace the HVAC control module. Refer to HVAC Module Assembly Replacement in HVAC. Did you complete the replacement? | -- | Go to Step 13 | -- |
13 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
