Tail Light Out, Then Back On

[angelg1674]

That's something to let the charging system know when a new battery is installed. I doubt it would have any effect on your taillight.

Yeah I sort of figured, I really thought that reprogramming the bcm would have fixed it but nope, I have to try to unplug the tail light and see what that does, I just don’t know how to check that tail light itself to see if it’s burned out, might have to buy a new one and just try my luck

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[1004ron]

My wife's V6 started this issue a few months ago and I incorrectly assumed it was the front indicator bulbs and changed them out and made sure all the connectors were clean and dry, but the galloping noise and rapid flash on the dashboard remained intermittent.

Just the other day I got the opportunity to walk around the car while it was doing that, and saw that it was the far left bar of the left tail light that wasn't working.

A new battery was installed in May 2021 and has never had any issue starting, but my battery tester shows a low settled voltage of 12.32v.
See screenshots of the test.

I put the battery maintainer on it through the night and the next day it misbehaved again.

I'll replace the battery if I had confirmation that's all that's needed.

The Service Manager said that he'll get back to me next week regarding the flashing of the BCM.

 

[1004ron]

The Service Dept’s can’t find that original SSM 45895 because it’s been supercded by SSM 47429 (which is the Official Ford SSM I have attached).

Too bad *some* of the Service Dept Techs can’t think OUTSIDE OF THE BOX... because the S550 taillight from 2015-2017 is the same; all they had to do was just go into their Ford site and select another Model Year and Vehicle Make without using a VIN and wa-la...... they would have found it.

My dealership is keen to help me but are reporting that SSM 47429 is no longer available.

Any chance you could help me help them find this?

Thanks.

 

[1004ron]

That is strange that your dealership said the SSM (TSB) is no longer available. I wonder what that even means. That doesn't make sense. In any case, the BCM needs to be updated IF it is the same problem I had.

This is the response I got:
checked Ford's Professional Technician System (PTS) website for the cited SSM 47429, and it's no longer available for callup.

I welcome any help I can get to help my dealership find this and apply it our Mustang.

 

[BadHorsy]

For what it's worth I paid $160 to have the BCMB reflashed in my 2015 today and it solved nothing. The left vertical bar on the passenger tail light is still bright like the brake is applied. Next up is a new tail light I guess. Battery is also brand new. $500 for a tail light assembly? *rolls eyes*

 

[1004ron]

For what it's worth I paid $160 to have the BCMB reflashed in my 2015 today and it solved nothing. The left vertical bar on the passenger tail light is still bright like the brake is applied. Next up is a new tail light I guess. Battery is also brand new. $500 for a tail light assembly? *rolls eyes*

I bought a rear lighting control module and before I could install it my wife wrote-off her 2015 V6.

If you'd like to try this module I can let you have it for $35 including USPS shipping.


FORD MUSTANG LIGHTING CONTROL MODULE OEM KR3T14D644BA

 

[BadHorsy]

I bought a rear lighting control module and before I could install it my wife wrote-off her 2015 V6.

If you'd like to try this module I can let you have it for $35 including USPS shipping.


FORD MUSTANG LIGHTING CONTROL MODULE OEM KR3T14D644BA

We have a convertible, so I'm not sure that would work but I appreciate the offer.

 

[BadHorsy]

Just to follow up on this. I have resolved our issue. Our inner most LED strip on the passenger taillight was always lit up bright like the brake was pressed while the others were in parking light mode. I had the SSM update done to our BMCB which did nothing in our case. I purchased a 72 hour pass to the Motorcraft site so I could get official wiring diagrams and understand just what is going on back there. Turns out, it's stupid simple.

Each tail light has a 12 volt input for parking lights which illuminates all three bars in a parking mode state. When you press the brakes or use the turn signal or hazards, there are three additional wires coming from the BCMB to each tail light. So when you step on the brakes, it applies 12 volts to each of the three inputs for the tail light so it lights up bright. When you use the turn signal it applies 12 volts to each of the three wires in a sequence to light up the tail light in turn signal mode. If you have a 12 volt power source you can unplug the tail light, apply ground to pin 6 (black wire I believe) and then apply 12 volts to pin 2 for park lights, pin 3, 4 and 5 for the bright turn signal/brake light.

I wanted to be sure I was replacing the right part before I bought a new tail light so I unhooked it from the car, ran my simple 12 volt tests above and the tail light worked exactly like it did IN the car. Clearing the BCMB of any issues. In our case we needed a new tail light. This might help someone else diagnose their tail light before stupidly spending $160 on an unneeded reprogram at the dealership.

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