Attempting to fix reverse lights (still not fixed), lost L&R brake lights as well (fixed)

[kronus]

I have a 2012 PPV, and when we bought it, the reverse lights were inoperative. I could pass inspection without them, so I ignored the issue as long as possible. Finally had some warm weather to work in today, so I started poking around and in the process of doing so, I’ve somehow lost my left and right brake lights as well.

I’ve verified it’s not the brake switch because my center mounted brake light still activates with the brake pedal. It also doesn’t seem to be a wiring/fuse issue because the rear corner lamps will light when turning on the headlights.

Here are the things I messed with today while trying to sort out the reverse lights:

1) Unplugged the drivers side tail lamp harness, checked for continuity, plugged it back in.

2) Unplugged the FSCM, shook some dirt out of the connector, plugged it back in.

3) Took the cover off of the MBEC and unplugged each connector looking for the reverse wire and plugged them back in. (I only unplugged one connector at a time, so I know they’re all in the correct positions.

4) Checked voltage across the reverse light pin (#8 in X10) and ground pin in (#1 in X16) with the truck in P, N, and R.

So now I’m totally lost as to why I have no L&R brake lights. Unless one of those connectors in the MBEC connects to the BCM (I assume it does) and by unplugging it, I messed up something in the BCM.

As a side note, the reverse pin (#8 in X10) had voltage across it regardless of gear - I thought this was odd considering I still have no reverse lights either (yes the bulbs are good).

 

[Doubeleive]

does it have a tow package? if so if nothing else can be made to work you could possibly patch into the tow harness wiring. just an idea

 

[kronus]

does it have a tow package? if so if nothing else can be made to work you could possibly patch into the tow harness wiring. just an idea

It’s a PPV, so from the factory, it had the harness for the trailer wiring tucked up under the bumper, but shortly after purchase, I replaced the bumper and connected the harness to the plug in new (to me) bumper.

 

[Doubeleive]

It’s a PPV, so from the factory, it had the harness for the trailer wiring tucked up under the bumper, but shortly after purchase, I replaced the bumper and car mnected the harness to the plug in new (to me) bumper.

Not quite sure I understand what you said, but if it does have the harness then you should be able to patch into it even if it is currently connected to something else

 

[Lancem]

Typically in the automotive world they switch the ground, don't know why but that is why you are seeing the 12 Volts across the plug, the neutral safety switch on the transmission is where I would look for your back up light problem. For the brake lights I would go back over what you have done and make sure you have good connections in the connectors you pulled apart.

 

[kronus]

Not quite sure I understand what you said, but if it does have the harness then you should be able to patch into it even if it is currently connected to something else

I was just explaining that the factory trailer harness wasn’t connected when I got the car and that I connected it once I purchased it.

However, I thought the reverse lights for the trailer connection patched from the main reverse signal, so if there’s no reverse signal to the tail lights, then the trailer wiring wouldn’t have it either, correct?

 

[Doubeleive]

I was just explaining that the factory trailer harness wasn’t connected when I got the car and that I connected it once I purchased it.

However, I thought the reverse lights for the trailer connection patched from the main reverse signal, so if there’s no reverse signal to the tail lights, then the trailer wiring wouldn’t have it either, correct?

depends on where the problem is in the wiring, you will need to test the trailer connector and see if it suffering the same problem or not, I was just suggesting this might be a solution if you cannot find where the problem is for the tail lights. At some point the trailer harness splits off from the main harness so it might work if the problem is after the split.

 

[kbuskill]

I would check ALL the fuses to start with.

There will be separate fuses for the brake lights. The rear "corner lights" as you call them, coming on with the headlights is a separate circuit. Those would be the parking or running lights.... separate fuse, seperate power.

Check all the fuses in the underhood fuse box and in the drivers side end of the dash.

 

[Wolfbraid]

Also check the wiring harness back there, if the PPV tapped into any of the lines, and when they removed equipment they might have broken a wire or connection

 

[Fless]

These trucks typically have separate fuses and circuits for trailer lights, each side (body) brake light, etc, so the suggestion that @kbuskill made would be a good place to start. Check the owner's manual to identify all the related fuses and either check them in-circuit for voltage or pull them and ohm them out to make sure they're not blown.

You can check voltage in-circuit by using the fuse test points: