tail and brake light issue

[beckya99]

Hi Jeff,

I have the EXACT same problem as you.

hazard/tag/blinker/brake/running and reverse lights all spaz out and do as the wish, depending on what combination of events are occuring (brake light with blinker, headlights and anything else going on, right blinker and nothing else, left blinker and nothing else, etc., etc.)

This is what I've done so far:

replaced all rear bulbs
replaced flasher relay under left hand dash (3 times)
checked ALL fuses and replaced anything relating to lights even if it was good
replaced right tail light circuit board
replaced all rear bulbs again
cut trailer light connector off and taped off
replaced multi function switch (blinker/cruise/wiper)

everything worked great for about a month, except my horn quit after a couple of days)

checked trailer light assembly
removed trailer light assembly/wiring
checked all grounds from rear electric harness to back bumper
'reset' system' via battery disconnect
'replaced' head light switch with used switch - seemed that lights got a little worse so replaced original

(then driver door lock flipped out and then passkey system locked fuel pump)

SO...

dismantled steering wheel/column area. Horn started working again

tried a variety of posted 'reset' methods on passkey system (to no avail)

dismantled driver door, removed trim cover from inside left (under interior fuses boxes) and checked ALL wiring/connectors and wiring between door and body and part way down under interior running board

replaced various and sundry fuses whether they needed it or not
replaced driver door lock actuator/solenoid
replaced key alarm/open door buzzer thingy above interior left fuse box
replaced lighter/car charger hook ups
replaced courtesy light in driver door, under dash and above ashtray
found a disconnected switch under passenger seat, pulled all bolts from passenger seat, tipped it back, reconnected it and checked other connections.
replaced stop light switch at top of break pedal
verified power to rear light assemblies
replaced both tail light circuit boards (bulb holders) again
replaced all rear light bulbs again (triple checking that bulbs are all correct and inserted properly

Results?

horn seems like it will work when steering wheel is reassembled
door/locks, etc work great and car starts again
buzzer works great
courtesy lights work great
lighter/car charger works great
passenger seat continues to work great
(driver's seat does, too except heating element is burned out)

TAIL LIGHTS STILL LOOK LIGHT ANEMIC AMBULANCE depending on combination of switches/actions at the moment involving brakes, blinkers and headlights.

This is blowing my mind. And I'm ready to blow the darn car to smithereens.

My question is this:

Exactly what is the ground wire that you found to be the problem and where is it located?

Oh yeah - lol - I just got an email from a Westfall GMC parts technician that says my vehicle does NOT have a body control module based on my VIN number, but EVERYTHING I have come acrossed says it does (I know it has an ECM for sure, but does it have a BCM?)

(I have a 99 Tahoe LT, 4WD, 4Door, 8 cyl, 350 5.7 vortex, OBS)

Thank you SO much for your time!

becky

 

[blackdiamond]

Check the ground on the left frame rail behind rear bumper. But there is no BCM on that vehicle. Either a grounding issue or that turn hazard switch is faulty again. very odd issue but when i look at the diagram thats the only 2 things that would cause your condition

 

[blackdiamond]

Check the grounds on your lower rad support also right and left i believe. the headlights use this ground.

 

[beckya99]

Check the grounds on your lower rad support also right and left i believe. the headlights use this ground.

tail and brake light issue

--------------------------------------------------------------------------------

okay, thank you! But...what's a lower rad support (and where is it)?

(smile)

becky

 

[beckya99]

Check the ground on the left frame rail behind rear bumper. But there is no BCM on that vehicle. Either a grounding issue or that turn hazard switch is faulty again. very odd issue but when i look at the diagram thats the only 2 things that would cause your condition

Also - I've changed the flasher relay (under dash at fuse box behind emergency brake) twice already.

My question is this: I've been using a Chilton's for my vecicle (among monstrous hours searching internet).

Last night I bought a Haynes manual Chevy/GMC for all models 1988-1998 and trucks/SUVS 92-2000)

On page 12-3, (pic 6-4) it shows an illustration for the 'flasher signal' at the above mentioned fuse box and illustration 6-9 (right next to it) shows a separate item called a hazard flasher that's allegedly located "behind the main light switch behind the dash panel".

It's the first I've heard/read/seen about a separate relay from the flasher relay.

It does not say if this applies to my specific vehicle, though.

Any ideas?

becky