Both of the turn indicators are blinking fast, the "flasher" ticking noise matches the turn indicators for the hyper flash. All the external lights are working normally.

I think using the left low beam headlight for the relay trigger in adding fog lights is the cause. I ran a lead from the low beam wire to the switch, which has two LEDs, one for "OFF" that shows the LOW BEAMS are on, and the other for when you turn the switch on and engage the relay driving the fog lights.

So I am assuming that having the one LED and the 150-250mA of current for the relay coil is setting off the computer to indicate it thinks there is a headlight problem. I wonder what the tolerance level is set for on the computer for this? I might be able to "trick-****" it by building an "opto-isolator" or something akin to it to drive the relay coil I suppose. Maybe a photoeye circuit to detect when the headlight is on.

Crap... I hate to think I will have to tear the dash apart, replace the headlamp switch, then have the dealer reprogram the computer for around $500-600 just to have fog lights.

Can you say STEALERSHIP?

 

CMHSL brake bulb is good?

 

Do you have an adapter in the trailer light harness near the spare tire for canopy lighting and/or for an in-bed 7-way receptacle? When I first had my bed canopy installed, the installer used an adapter between the wire harness and the 7-way receptacle in the bumper. Same symptom as you described. I removed the adaptor and hard-wired the CHMSL, and the problem went away.

 

I am fairly certain it is the tapping in on the left low beam headlight the relay coil and the switch with the LED indicators for the fog lights that did it. It should be only 150-250mA current draw but I suspect the computer can detect it.

I am currently looking at the opto-isolator circuit option. It only draws 5mA. You supply it withe +/-12vdc, it has a sense line to tie into the li-beam wire, then has a tiny relay powered separately to operate the fog light relay coil. I am thinking the computer isn't set to detect something as low as 5mA of current change. An opto-isolator runs about $10.00 + shipping.

 

So I had the hyper flash on my 2020 STX f350. It was a bulb and the bulb worked.

Crazy as it sounds replacing a rear driver turn bulb fixed it. The bulb was malfunctioning some way but still lighted up.

I did notice it ever so slightly flicker the last time before replacing when we were testing everything. But man we tested the bulbs several times with different people at work trying to figure it out.

 

Do you have LED or incandescent lights (headlight and turn signal)? The BCM typically triggers the bulb-out flash because the load is too small (for incandescent). I don't know how it determines the LED is out (may be sophisticated).

What is puzzling is the headlight drive circuits should not determine a hyperflash condition. If the BCM thinks the headlight is burned out it will usually post a message in the display or do nothing at all.

First, I assume you disconnected the trigger wire and everything is OK. Next, bypass the lighted switch and see what happens when the fog lights are turned on from the relay in the fog light harness and the switch illumination is bypassed.

A smaller trigger load is unlikely to do anything, but the lighted switch circuit may be the problem.

The elegant solution would be to use Forscan to turn on the fog light function. Use wiring diagrams to tap into the fog light power feed and connect that to you aftermarket light relay. You may have to buy a headlight switch with the fog light button (I don't know how your truck turns on OEM lights). The switch sends a message on the CAN to communicate with the BCM so no extra wiring is possible.

 

Yeah. Trying to avoid all that extra cost of a new headlight switch, tearing the dash panel part to install it, then having to have the dealer reprogram it as I have no FORSCAN software nor adapters to connect it to my computer. The dealer would probably leave me a paraplegic crawling out their door and into my truck after all that. They'd probably tell me I need a new bumper and the Ford fog lights instead of the halogen Hellas....

I will give the opto-isolator a try. I am Everything was fine until the fog light relay coil and the switch with the LED indicators in it was added to the left headlight low beam circuit. I verified it is the low beam head light circuit. Doesn't do it on high beam nor when the head lights are off or just the parking light are on. I put in a harness extension with male to female connectors so I wouldn't have to mess with the actual truck wiring. SO all I have to do is unplug that and plug the stock harness back into the headlight bulb to undo the mod. I didn't check it with the DRLs running during a sunny day.