Circuit Description
The solar/twilight sensor is a photo-electric cell that provides two inputs to the heater and A/C control system. The input for the sunload is at terminal 3 of the heater and A/C control. This is used by the controller for temperature control compensation based on additional heat from the sun (sunload.) The input for the twilight sentinel is at terminal 2. The twilight sentinel input is then processed by the controller and sent to the Body Control Module (BCM).
Conditions for Setting the DTC
The heater and A/C control continuously monitors CKT X812. DTC 39 will set when the circuit stays above 5.5 V for 200 ms.
Action Taken When the DTC Sets
| • | Stores a DTC 39 in the heater and A/C control memory. |
| • | The system will default to a assumed value of no solar heat (darkness). |
Conditions for Clearing the DTC
| • | The conditions for the fault are no longer present. |
| • | Using a scan tool. |
| • | A history DTC will clear after 20 consecutive ignition cycles if the condition for the fault is no longer present. |
Diagnostic Aids
| • | If the DTC is a history or intermittent. Try performing the tests shown while moving the wiring harnesses and connectors, this can often cause the malfunction to appear. |
| • | Visually inspect sensor connector and harness for damage, corrosion or water intrusion. |
| • | Check for adequate terminal tension, mis-routed harness, rubbed through wire insulation, and broken wire(s) inside the insulation. |
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the HVAC Systems Diagnostic System Check? | -- | Go to Diagnostic System Check | |
Does the voltage measure greater than the specified value? | 5 V | Go to Diagnostic Aids | ||
3 |
Did you find and correct the condition? | -- | ||
4 |
Does the DTC reset? | -- | System OK | |
5 | Inspect for poor connections at the harness connector of the heater and A/C control. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find and correct the condition? | -- | ||
6 | Replace and program the heater and A/C control. Did you complete the replacement? | -- | -- |
