B160F-92

B160F-92-TWILIGHT/AMBIENT LIGHT SENSOR INPUT - PERFORMANCE OR INCORRECT OPERATION

For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The HVAC A/C heater control uses a variety of sensors to adjust HVAC operation to obtain optimal performance. These sensors are continuously monitored by the A/C heater control to assure that they are in range. An active Diagnostic Trouble Code (DTC) indicates that a sensor is out of range. A stored DTC indicates that the sensor was out of range but is currently within range.

A sun sensor is not a thermistor type sensor but is more accurately a photo diode. For this reason the sun sensor responds to sun light intensity rather than temperature. The sun sensor converts sunlight intensity to an electrical voltage which provides data to the A/C heater control to help determine proper mode and blend-air door positions and blower motor speeds. The sun sensor assembly is also used to sense day and night conditions for automatic headlight control if equipped.

- When Monitored:
Continuously with the ignition on.

- Set Condition:
If the A/C Heater Control detects on the Auto Headlamps Signal circuit an input voltage less than 1.05 volts and greater than 0.25 volt for period of two seconds or more. This DTC has a de-maturing time of 20 ms. If the DTCs status changes from active to stored, the DTC will stay in memory for 100 ignition cycles.





Always perform the HVAC Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview.

Diagnostic Test

1. CHECK IF THE DTC IS ACTIVE
1. Ignition on, engine not running.
2. With the scan tool, read HVAC DTCs.

Is this DTC active?

Yes

- Go To 2

No

- Go To 4

2. CHECK (L24) AUTO HEADLAMPS SIGNAL CIRCUIT FOR A SHORT TO GROUND




1. Turn the ignition off to the lock position.
2. Disconnect the A/C Heater Control C2 harness connector.
3. Disconnect the Sun Sensor harness connector.
4. Measure the resistance between ground and he (L24) Auto Headlamps Signal circuit.

Is the resistance below 100k Ohms?

Yes

- Repair the (L24) Auto Headlamps Signal circuit for a short to ground or high resistance.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Go To 3

3. CHECK THE A/C HEATER CONTROL
1. Replace the Sun Sensor. Sun Sensor - Removal.
2. Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

Did this DTC reset while performing the HVAC Verification Test?

Yes

- Replace and program the A/C Heater Control. A/C And Heater Control - Removal.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Test complete.

4. CHECK THE WIRING AND CONNECTORS
1. The conditions necessary to set the DTC are not present at this time.
2. Using the scan tool, check the Environmental Data to help identify the conditions in which the DTC was set.
3. Using the wiring diagrams as a guide, check all related splices and connectors for signs of water intrusion, corrosion, pushed out or bent terminals, and correct pin tension.
4. Wiggle the wiring and connectors while checking for shorted and open circuits.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Test complete.