Mustang S550 - Taillight Issue On and Off!

[JohnDoe]

Apparently, the origin, or the cause of tail light issues is not caused by any one particular failure. One member ( duckeydave) on the 6th gen forum replaced his tail light...problem fixed.

Several members re-programmed the BCMB. Some lights were fixed others were not.

Currently, my BCMB will not accept any updates. Dealer says to replace the BCMB. Car currently in shop. I don't know what I'll do if the new BCMB
does not work. Dealer will need to contact a FORD Factory Rep. probably. Will keep everyone posted.

I'm really hoping it's just a tri-bar board that is out, because the entire left tail light use to go out up until I disconnected my sequencer harnesses and that's how I discovered the in-op inside tribar.

Will find out soon once my new set of tail lights come in.

Sponsored

 

[ezracer]

I'm really hoping it's just a tri-bar board that is out, because the entire left tail light use to go out up until I disconnected my sequencer harnesses and that's how I discovered the in-op inside tribar.

Will find out soon once my new set of tail lights come in.

OK so I had a slightly different issue. My left tail light would not sequence properly.

**Reprogrammed BCMB...no luck
**Installed NEW BCMB...no luck ( dealer did not charge me)
**Installed NEW tail light...SUCCESS!!!!!!!!!!!!!

Good luck with yours. From my limited experience ( I'm no Technician ).... the BCMB generates a signal to the
tail lights and then the circuitry inside the light operates the light "PROPERLY".

 

[JohnDoe]

Tried new aftermarket tail lights and the left turn signal didn't work for it, so it has to be a bad control module. I just ordered a 2017 take off BCM from ebay for $50. It only has 1500 miles on it, so I'm crossing my fingers that this will work. I really do not want to pay Ford $140 just to figure out what's wrong first, then even more to flash it

 

[JohnDoe]

How do I go about programming the bcmb? Can’t I just plug in the replacement bcmb and see what happens?

 

[JohnDoe]

Got all my tribars working again by just simply swapping out the BCMB with the takeoff I purchased but the only problem is it wasn’t from a convertible so I couldn’t operate my top. Now the search for a BCMB from a convertible begins.

 

[FourdBanger18]

Looks like I am going to have to go this route. Will keep updating

 

[BadHorsy]

Does anyone TRULY understand this fault and isn’t guessing at fixes? Our 2015 just started doing this with the passenger tail light. With the car off the left most bar is bright like the brake pedal is depressed. The right most bar is out and the turn signal only lights both left most bars and you get the fast flash signal on the gauge cluster.

If this is related to a low voltage condition, why doesn’t it resolve with the engine running and battery/alternator voltage at 14.4volts? We’ve only had the car for a few months but it’s only got 9000 miles on it. Worked flawlessly all summer/fall. One cold drive (50’s) and now the BCMB or tail light assembly is unhappy.

I’ll ask our dealer to recalibrate the BCMB with the TSB above once it’s warmer but I really want to understand what the cause is. Why does the BCMB hold onto this previous low voltage state? I’ve had the car on a battery tender for days now and the battery is at 13 volts and I still get the same tail light fault. If this was SOLELY related to low voltage, why is the problem not clearing? I’m not getting any check engine light although I’m not sure if those associated codes above would set the CEL or not.

The car starts just fine, the battery is two years old and while I’m tempted to swap the battery, it seems unnecessary just to resolve a brake light issue that I can’t say 100% is related to voltage.

 

[ezracer]

More than likely, you need a new taillight assembly. I had the same problem but it was with sequencing. Tried everything, including BCM re-programming. Replaced taillight with new unit. Fixed!!

 

[1004ron]

Got all my tribars working again by just simply swapping out the BCMB with the takeoff I purchased but the only problem is it wasn’t from a convertible so I couldn’t operate my top. Now the search for a BCMB from a convertible begins.

All the dealerships contacted no longer have the BCM update files, so now I'm looking to do what was successful for you but I cant find a used 2017+ BCMB on eBay.

Where is this module located?

Also, is that photo of the convertible BCM?
Edit:
Found it.
https://www.mustang6g.com/forums/threads/body-control-module-removal.119102/

Sponsored