DTC 40

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. This Input is processed by the controller and sent to the Body Control Module (BCM).

Conditions for Setting the DTC

The voltage on circuits P11 or P111 significantly rises above 400 mV for 200 ms.

Action Taken When the DTC Sets

- Stores a DTC 40 in the heater and A/C control memory.
- The system will default to a assumed value of no solar heat (darkness).
- DTCs 10, 12, 14, 28, 39,55 and 169 may also appear when DTC 40 sets.

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

- In the event that the multiple DTCs set, first follow the repair procedures in the diagnostic table for DTC 40. If some or all of the multiple DTCs reappear after repairing the cause of DTC 40, follow the repair procedures given for the appropriate DTC.
- 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 end 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.

2. This step checks the ground circuit of the solar/twilight sensor. A normal reading should be approximately 400 mV or less. A significantly higher voltage reading indicates a circuit problem.
3. This step isolates the circuit and a check is made for a short to battery.
4. This step rechecks the circuit for a short to battery but with the ignition switch ON.
6. If no apparent circuit problem was found in the previous steps and the DTC resets, the most likely cause is a heater and A/C control malfunction.