In other vehicles, I've had similar problems caused by simple oxidation/corrosion in the turn signal light socket itself. Have you checked that possibility? (Could be front or rear - but if the cruise is effected, it's more likely the rear).

- Jack

 

I started checking out the tail lights and High mount brake again. I figured out that with the park lights on only and both tail light bulbs in their sockets the high mount bulb stays on bright as if the brakes are engaged. I pulled a tail light to check voltage at the socket and got ~6.8v. However, if I leave the meter attached and pull the opposite tail light bulb the meter jumps from 6.8v to ~11.8v. This is interchangable from driver to pass sides. The high mount also dims slightly when I pull a tail light bulb.
I also tried pulling the high mount bulb out with the park lights on and the tail lights went out completely. I feel like this should be telling me something but I dont know what.
BTW, what is "swag"?
Sorry if this is all confusing. Im confused as hell so I can only imagine what its like reading this. Thanks for the help though.

 

Did you ever check the sockets for a ground ?

If you have the CHMSL bulb always on, and when you pull it, the tail lamps go out ( parking and brake ?? ) then that tells me the tail lamp housing is using the CHMSL for the path to ground, which is a high resistance ground, and would cause the voltage drop you are seeing ( ~ 6 V )

The CHMSL on, as if the brakes are on, is why the CC does not work.

When you check the sockets for ground, do as Jack posted, check front and rear condition of the socket. Pull all the bulbs ( including the CHMSL ) when you do this.

Make sure you have a good ground to test against ( trailer tow adapter ? need to confirm to the lug in the frame ). Front is easy, the battery is right there.

 

I have not checked the sockets for ground. I will do that my first day off which will be thurs (I dont have much daylight when I get home from work). Today though I think I might have gotten a little closer anyway. I dropped my spare tire again and disconnected the large harness that goes to trailer wiring and tail lights. Disconnecting that harness turned off my high mount and made it start working again only when the brakes are engaged.
Once I had that going for me I plugged the large harness back in and unplugged the smaller harness for the tail lights. Once again, the high mount went out and only comes on when the brakes are engaged (which was nice). That must mean that my issue lies between the tail lights and the small wiring harness right? Do all of the rear lights use the one ground wire that is screwed to the cross member above the spare?

 

looking at the 2006 EVTM, the tail lamps have different grounds, including the one for the trailer brake module.

Speaking of Brake controller, do you have one installed ??

Trailer Tow Adapter



Turn / Stop Lamps - Rear of truck

 

I do not have an electric trailer brake controller. My boat trailer has surge brakes and I only use the 4pin connector. I will be checking all the wires from the tail lights to the small harness I unplugged. Hoping to find some wear on a couple of wires back there.

 

Alright, I checked the sockets for ground several times and got ~4ohm. I also decided to check for ground by unplugging the rear lights from the harness that only contains wiring for tail, reverse and liscense plates bulbs. Checking for ground at the harness end that runs to the front of the truck gave me an ~7K-ohm reading. How can I be getting a good ohm reading at the socket but testing from the harness plug to the front of the truck says its bad? Im using the same tester and made sure my ground was good several times.

 

This thread caught my eye, especially the trailer hitch wiring harness illustration that
SSCULLY posted. I just had an unusual situation with my turn signals on my 2001 Supercrew. There was interaction between the brake lights and the turn signals. If either the left or right turn signals were selected both rear lights would flash as would the high brake light, the front turn signal lights functioned properly. As soon as you put your foot on the brake pedal all turn signal lights would freeze. The hazard flashers functioned properly.
I did a search on the forum and found this thread and it jogged my memory. When the truck was new I wired in one of those square lights that fit into the trailer hitch receiver tapping off the back of the stock electrical receptacle for a trailer. I wired the light to the brake light wire so it would act the same as the high brake light. Once I saw the wiring harness illustration I thought that maybe over time something got corroded or shorted in that area. I unplugged the connector and sure enough everything went back to normal. I haven't dug any further yet to see what in the wiring actually went bad, I am very happy not to have to dig into the MFS at this point. Thanks for all the great info posted in this forum.

 

Well I can officially join this thread. Today I turned on my left turn signal and it acted like it just downed a red bull. My left turn signal exterior lights, and dash illuminated arrow are blinking about twice as fast. I purchased a 4 star GE warranty and hopefully that'll cover the trip to the stealership. Anyone ever find any resolve?

 

double post

 

Check to make sure both the exterior front and rear left turn bulbs are working. One may just be out.

 

Well problem fixed. Everyone kept talking about checking bulbs so I watched my lights from the outside with the left blinker turned on and the back bulb wasn't flashing. The bulb wasn't burned out, it just wouldn't flash. I still ran up to advance auto parts and picked up a new bulb, 3057 i think. It was only 5 bucks for 2 bulbs. Switched the bulbs and now it works like a charm. So even though the bulb wasn't burned out, it still wouldn't flash. Oh well, to any that have this problem whatever bulb isn't flashing just swap it out and see if it works like it did for me.

 

Had the same exact prloblems as the original poster. Same symptoms. Was starting to really make me mad. Found out the remote starter installer cut the brake wire completely and it fell apart when i took the tape off. Anyway i started looking at connections going back to the tail lights. Also noticed that the third brake light was lit with just the running lights on. Well wiggled the bottom connection on the frame under the driver area. Problem goes away. So I take it apart and find some rusty connections. Some dielectric grease and copper strands to make a tight connections and all is well. Also fixed the cruise shutting off when you use a blinker and the windows started working again.

 

Steelfan26. Have you ever resolved your issues? Have all the same issues now.

 

Kippy/Steelfan26 - you guys ever find anything out? Same issues here!