Gave someone a jump, now brake lights stuck on when headlights on.....how do I track down this bad ground? (1 Viewer)

[Francis K]

Hi guys, another half banana masterpiece from yours truly over here....

Relevant info....I have rear aftermarket LED tail lamps as well as LED's in my ARB front, half wired to the turn signal and the other half to the DRL, also have remote start installed.


Gave someone a jump recently and since then when I hit the brakes it turns on my DRL and all my interior dash lights on even with the truck off. With my headlights on my brake lights are stuck on including the 3rd brake light, also my cruise doesn't work with my lights on or shuts down when I turn my blinker on and my remote start doesn't work at all.

Did some research and saw lots of others have had this issue and attributed to a bad ground for the tail lights. Read that I could test this by removing the bulbs in the tail lights and seeing if it solved it, I removed both tail lights and all the bulbs and the issue persists, also installed stock bulbs and no change. Then though maybe it was my front LED's in the ARB which are wired to my DRL/turn signals so I removed the bulbs from those as well and no luck.


So is this process of elimination correct or am I way off here? Also disconnected the trailer harness, no change. Also checked the wiring on the back of the bulb sockets, no change. Ground under the truck in the center rear also good....

 

[Francis K]

Popped the rear panel....looks pretty clean in there you guys see anything I don't? No idea what to do from here, she's my DD I'm kinda stuck at the moment....

 

[Francis K]

Thought I had this sorted but the chase is on again, also my rear wiper blade was running on it's own the other day.

Swapping back to OEM tails didn't fix it, removing the LED's in the ARB didn't fix it. The rear ground under the tailgate looks fine. The grounds near the battery look fine as well as on the other side.

Where do I go from here fellas? What haven't I checked? Perhaps where that ground in the rear leads from is disconnected....but where would I find that wire?

 

[DivByZero]

That's... worrying.

OK, here's something I doubt you've tried. Pull the right side kick panel. Find the 3-4 connectors (depending on year model) that lead to the floor harness and the door harness. Pull them. Go to the rear left cargo area, and pull all the connectors there, not just to the lights, but the ones to the floor harness that runs out under the rear floor of your vehicle. They're all there in the back left. That will isolate everything on the rear of your vehicle except the fuel pump and the two left door harnesses. Obviously you now have no rear lights at all, but check if your other electrical gremlins have now disappeared. If so, connect back one connector at a time to narrow down what one causes it to break.

If you still have problems with all these harnesses pulled, report back, and we've determined the problem is upstream of those connectors.

 

[Squash]

Unbolt the jack bracket and down below will be more connections. Check for corrosion and or blue gunk.
If your highways get salted there is a good chance that salt has mucked you up.
Your rear wiper motor can be damp inside causing an unwanted ground.

 

[Francis K]

Hi guys, okay I went in there and messed with everything I could find and the issue went away. Figured I knocked it out perhaps something was just loose or dirty.

But it came back for one day last week, i didn't have time to mess with it and it went away. Today it's back again, same issue....both days it was raining.


So pretty much any time the truck is wet I get this issue, that correlated with the other instances as well. Then when I pull the truck into my warehouse it dries off and problem gone, with me thinking I fixed it!

 

[leonard_nemoy]

I had the auto rear wiper whenever it was wet. There was a connector underneath my jack holder in the rear quarter panel. This connector was very crusty and dirty from the extra exposure it received from trimmed fenders not being sealed.

I cleaned the connector well and got my rear fenders sealed and the problem has been resolved.

 

[Francis K]

Hi guys, just updated for the next jack wagon like me who it may help.

After a lot of trial and error and with all the help here I ultimately determined my rear window trim was leaking and causing the issue. I installed new louvers and rubber, leak is gone and so is the problem even after heavy rains and carwashes. Also cleaned all the connectors one by one for good measure....all set.

Thanks to everyone for the replies!

 

[LongDuck]

I was going to suggest a young priest and an old priest, but thanks for posting back how you fixed it!

 

[60 toy ota]

I had the auto rear wiper whenever it was wet.

I see no problem here haha.

To the op, thanks for posting about your final resolution and glad you got to the bottom of it!