Nighttime Rear Running Lights Not On While Headlights are On

[bcl0404]

Apologies if this is a really simple answer, but upon searching, I didn't see a similar issue.

My nighttime rear running lights do not illuminate in spite of headlights being ON (both auto and manual). But, all of the rear bulbs function when appropriately triggered (the left, right, and 3rd brake lights all illuminate when braking and the rear white reverse lights illuminate when in reverse).

Any suggestions?

Thanks in advance

Sponsored

 

[Crash98]

Did you try putting it in gear and checking?

 

[bcl0404]

Yessir. I’m scratching my head here. If the wiring harness was dead, my guess would be that none of the lights would work at all?

 

[bcl0404]

Any ideas? I really don't want to have to take it to the dealer for them to have the vehicle for 2 days, conclude something ridiculous like it needing new bulbs (the bulbs work), and for the problem to not actually be solved. 15 trips back to the dealer later, they might swap the wiring harness...

 

[330SMG]

Apologies if this is a really simple answer, but upon searching, I didn't see a similar issue.

My nighttime rear running lights do not illuminate in spite of headlights being ON (both auto and manual). But, all of the rear bulbs function when appropriately triggered (the left, right, and 3rd brake lights all illuminate when braking and the rear white reverse lights illuminate when in reverse).

Any suggestions?

Thanks in advance

Are you sure you have the headlights on. See way too many people with DRLS on thinking they have headlights.
Do you have brake lights?
If they are on get a tester and pull a bulb to see if there is 12 volt.
If not check to see if seperate fuse.
If not then check connection from taillights back to dash.
If can figure it out goto dealer.

 

[Ground_zero298]

They won’t turn on sitting in park. They should turn on with key unlock and in parking lights only mode. If they don’t turn on with those may have to hit the dealership.

 

[bcl0404]

They won’t turn on sitting in park. They should turn on with key unlock and in parking lights only mode. If they don’t turn on with those may have to hit the dealership.

I get no "red glow" when the parking lights or headlights are activated (but the red brake light bulb illuminates when the brake pedal is depressed and the turn signal is activated) [I have a Black Diamond with the standard light housing (not the signature housing)], which is what is confusing me.

 

[Ground_zero298]

Any chance a bad bulb could cause it? Lights are easy to remove. I did a post for a light swap if you want to look at it for removal.

https://www.bronco6g.com/forum/threads/archaic-tail-light-full-led-install.59837/

I know there are setting for the lights in for scan also. Wonder if an update or something may have screwed em up. Or maybe programmed for led in the settings.

 

[Ramble_Offroad]

I saw a Bronco in town last week. Headlights on. Nighttime. No taillights whatsoever.

 

[bcl0404]

I saw a Bronco in town last week. Headlights on. Nighttime. No taillights whatsoever.

^^^I'm in CT, otherwise I would have said it was me .

I will pull apart the light housing to access the bulbs, but the bulbs all function for everything except the "running lights" (there is no tail light "glow" when the headlights are on).

Is there a specific fuse for the rear lights? But, I wouldn't think a fuse is blown if the bulbs function for braking/turning.

 

[AKBronc49]

Is there a specific fuse for the rear lights? But, I wouldn't think a fuse is blown if the bulbs function for braking/turning.

Completely possible, your incandescent bulbs in your stop/tail/turn lamps has two filaments, one is dim for parking lights and one is bright for your brake/turn function. They are separate.

Parking lamp fuse would be the first thing to look at.

 

[bcl0404]

Completely possible, your incandescent bulbs in your stop/tail/turn lamps has two filaments, one is dim for parking lights and one is bright for your brake/turn function. They are separate.

Parking lamp fuse would be the first thing to look at.

Any idea which fuse # it is? I looked at the diagram and didn't see that was obviously for the rear lights/parking lights.

 

[AKBronc49]

With everything being BCM controlled they may not have a fuse for it.

Unfortunately this is a warranty issue and you'll need to schedule it for service.

Do you have the tow package?

 

[Ducati1098]

Any idea which fuse # it is? I looked at the diagram and didn't see that was obviously for the rear lights/parking lights.

With everything being BCM controlled they may not have a fuse for it.

Unfortunately this is a warranty issue and you'll need to schedule it for service.

Do you have the tow package?

Correct, there is no fuse to check. The lights are controlled by a FET in the BCM.

 

[AKBronc49]

Correct, there is no fuse to check. The lights are controlled by a FET in the BCM.

I thought about it after the fact, I work in the business of upfitting new work trucks and we've blown up a couple BCM's learning....lol

Sponsored