Related to the work you were doing the Light Out is tested during the Actuator test. Just could not find if that test is manually run or automatically run, it checks for shorts in the system. My guess is that's manually run?
I will flip this info below physically vs how it's listed in the text.
Also:
FCM = Front Control Module
CHMSL= Center High Mounted Stop Lamp
FCM is all done over communications so grounds and the sort could play into that deal.
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Actuator Test - Each time the cluster is put through the actuator test, the lamp out indicator will be turned on, then off again during the VFD portion of the test to confirm the functionality of the VFD and the cluster control circuitry.
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Lamp Out Indicator Lamp-On Message - Each time the cluster receives a lamp out indicator lamp-on message from the FCM indicating that an inoperative headlamp (low or high beam), turn signal lamp, or brake lamp (excluding Center High Mounted Stop Lamp [CHMSL]) circuit has been detected with the ignition switch in the On position, the lamp out indicator is illuminated solid. The indicator remains illuminated until the cluster receives a lamp out indicator lamp-off message from the FCM or until the ignition switch is turned to the Off position, whichever occurs first.
If the lamp-on message is received when the ignition is first turned to the On position, the lamp out indicator is flashed at a fast rate (1 Hertz) for about thirty seconds before illuminating solid.
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Here is a copy paste deal on the Electronic Back Light (EBL) flashing as well,if equipped, that provides some additional diagnostic.
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HVAC DOOR CALIBRATION
The HVAC Door Recalibration:
- is actuated with the DRBIII(R).
- homes and repositions door actuators
- monitors for door span faults.
- indicates an outcome by displaying one or more messages on the DRBIII(R).
For vehicles equipped with electric backlight (EBL), running the HVAC Door Recalibration will cause the EBL status indicator to flash. If recalibration fails, the EBL status indicator will continue to flash until either the system passes recalibration or the ignition key is cycled. When the EBL status indicator is flashing, it will not indicate EBL operating status. However, the EBL mode switch will continue to function normally. When the EBL status indicator is flashing, the A/C status indicator will not function. However, the A/C mode switch will continue to function normally.
For vehicles not equipped with electric backlight (EBL), no status indicator will flash when running the HVAC Door Recalibration. If recalibration fails, the A/C status indicator will not function, however, the A/C mode switch will continue to function normally.