Stock 2016 King Ranch, Halogen headlamps and brights. This morning the RH bright (lower) began to flicker on and off without having turned the brights on. Truck does have the auto-dim feature. Heavy rain the last couple of days, but haven't driven in it, nor is moisture a new thing in this country. Have not driven through standing water. An accident three weeks ago took out the RH fog lamp.The flicker occurs whether the remaining fog lamp is lit or not. With the lights on bright, the flickering does not occur. The LH bright operates normally.

Questions:
From what source is the lamp receiving the voltage to illuminate when the lights are dimmed?
What occurred to initiate the issue at this time?

 

Power comes from the Body Control Module (BCM) for all lights. The first thing I would do is pull the passenger side kick panel and inspect the BCM, which is behind that panel, looking for water. The cabin fuse panel is part of the BCM. You could also pull the PS scuff plate to see if any water is in the cable tray that runs down the cab floor.

Does your truck have a roof opening? The drains can get plugged or, in some cases, even disconnected. Water can then run down the A-pillar and get into the BCM.

 

Thanks for the input and ideas. I did pull the passenger kick panel as well as inspecting connectors and fuse panel. No moisture was noted. The truck does have the moon roof, but all appears to be servicable and satisfactory in that area.

A change has occurred. Now the RH dim and brights lamps are inop. Due to the accident in which the fog lamp was damaged, I've wondered if some chafing between power wires for each bulb has taken place. In such a happenstance, perhaps voltage from the low beam could have entered the high beam to create the flicking issue? It is speculation, but I have to get the bottom of it. Thanks again.

 

That`s odd, I just looked at the window sticker on my `15 King Ranch & it states that LED heads & tails are standard equipment. Did that change for the `16 model year?

 

I'm pretty sure that is my error. Apologies. Thanks for the correction.

 

Headlamps are powered and controlled by the BCM. The lamp circuits are all protected from over-current by FETs (Field Effect Transistor). In the event of an over-current the FET shuts the circuit off. The FET then auto-resets on the next ignition cycle (Off-On). If the FET trips too many times due to a continuing problem, the BCM disables the circuit, issues a DTC, and the circuit remains off until the problem is corrected and the DTC cleared. A DTC scan with FORScan or a diagnostic scan tool would help to determine the problem or problems, especially since the vehicle was in an accident.

The LED headlamps have internal ballasts to power the LEDs. Headlamp flickering could be an indication that the voltage getting to the ballast is low. Check the harnesses and connectors for damage and make sure all the connectors are completely latched together.