Hi all - new member but have exhausted the search function for this one. So here I am!

Few weeks ago I had the similar issue of some members where both tail lights stopped working, #20 fuse blown, replace it and back right tail light stays on, then start vehicle and fuse blows. After searching and replacing all the bulbs this led me to think BCM. Ordered a new one, took it to GM dealer to have rescanned, and yay I have tail lights. However, when leaving the parking lot and turning to the right with blinker on I started getting hyper-flash. So went into nearby parking lot and started messing with it. Only does it with right turn signal is on and turning right. Left turn signal and turning left no issues at all. Ended up taking it back to dealer and they said it must be a bad BCM, replaced it under AC Delco warranty, aaaaaannd still doing the same exact thing. I've checked the trailer/tow wiring harness that is common short by the door and found nothing (I actually re-routed this early on thanks to reading forum ahead of time) so my question is where else should I look for a bad short or ground? I should also note when it does hyper-flash the right rear brake light does not flash only the front turn signal, which makes me think short somewhere on a body/frame.

Any help appreciated and hopefully if someone else ends up having this issue will be able to document and save for future use.

 

You did not provide us year and miles???????

All of them are getting OLD, which even if not driven, degrades electrical connections. The first mod to do to every H3/H3T is to replace the factory crappy azzed Battery Terminal Connectors with a quality aftermarket set like Stingers or your favorite brand.

Next, since your issue is at the rear, check and clean the rear brake circuit ground(s) and make sure the tail light wires to the Right side for cracks, frays, and the physical connections to the tail light sockets. Clean the sockets with electrical contact cleaner. Change the right side turn signal/brake bulb and see what that does.

 

It is a 2008 with 95k miles. Thanks for tip on the battery terminal connectors, those are good right now. I've changed the bulbs and put dielectric grease in them during the process. Where are the rear brake circuit grounds located is there a good diagram of this? I will inspect those tonight if I can locate them and see if there is a loose ground bolt perhaps. Not sure best way to inspect wires past the pigtails coming out of the rear fender either. Perhaps pull the inner fender liners?

 

Dielectric grease should NOT be used in light sockets. It is an insulator against corrosion, not a conductor. By your description you did not mention electrical contact cleaner, which is what you are supposed to use first (I would use a new bulb) then follow with grease around the outside edge of the bulb away from the contacts.

How are your Battery Terminal Connectors "good right now"? Unless you changed them, they are NOT good and are the #1 known cause for electrical Gremlins. Look it up. You would be surprised how many things go wrong because of minute voltage inconsistencies to the BCM and PCM caused by bad battery connections.


Ground for rear lights is position G420 (near license plate wires) #6 in the below diagram.

 

I have the same issue, but no one seems to come back to the forum and post their fix.
What did you determine? Thanks

 

Welcome to HF.

FIVE YEAR OLD THREAD ALERT!!!!!!! READ: Old Threads/'Necro-Bumping'

We have no idea if you took the steps already recommended in this thread. After you have, come back and post a New Thread.

Closed this old dog, and the other even OLDER Thread you resurrected from long dead.