Flickering lights

[solli5pack]

mirror auto dimming is normally controlled by the sensor in the rear view mirror. (when light shines thru the rear window the sensor detects it and dims the rearview mirror and drivers side mirror) the sensor on the backside of the mirror (facing forward) also detects ambient light and dims the interior lighting, cluster, radio.
do you have the stock radio or is it aftermarket? and if it is stock does everything work? I believe the stock amp operation communication is thru the radio so if it is aftermarket that might explain why you are unable to communicate with the amp or perhaps you are selecting the wrong radio or amp with the tech2?
headlights I have pretty much always ran HID or other aftermarket lights and have just ran the ground from the headlight harness right to the frame. (leaving anything else intact)

Stock radio and everything seems to be working fine. I was just messing around one day with the Tech-2 and noticed I couldn't comunicate with the amp. It's another issues I've been putting up with for a few months. I need to do some testing from the amp which I believe is under the center console.

 

[solli5pack]

Please do report back on this. Also would like to know about your ground testing procedure. I've read that the stud for this ground is known to be an issue on gmt900 trucks. Something about insulation getting caught in it during assembly and or that it becomes loose. The bad part about it is that to get to it you have to remove the dash which isn't fun. You see it or access it by removing the driver's side a pillar trim piece. I've tried.

Right now I'm just going to test the ground from the headlight switch connector and see what I get. The procedure I'm using is with a multi meter putting on probe on the negative battery terminal and the other probe on the ground I want to test. With the meter on ohms the resistance should be pretty close to zero. Also need to check for voltage which should be pretty close to zero also. I'm probably going to need a jumper wire to reach from the battery to some of these other grounds not in the engine compartment.

 

[Joseph Garcia]

GREAT troubleshooting discussion! I've learned a lot just by observing.

 

[solli5pack]

Little update not related to the flickering lights. I'm standing in front of my house looking at the Yukon thinking about what @Doubeleive said about the sensors on the mirror so I walked over to check them out. Low and behold there's a sticker placed over the square front facing sensor. I peeled it off carefully and it looks like it's a oil change reminder sticker from a Cadillac dealership dated 10/30/2008! Lol. Is it possible at this trucks first oil change somebody covered I guess a semi important sensor? Not sure what kind of change I'm going to see but the lighting and mirrors have definitely been acting wierd on this truck.

 

[Doubeleive]

Little update not related to the flickering lights. I'm standing in front of my house looking at the Yukon thinking about what @Doubeleive said about the sensors on the mirror so I walked over to check them out. Low and behold there's a sticker placed over the square front facing sensor. I peeled it off carefully and it looks like it's a oil change reminder sticker from a Cadillac dealership dated 10/30/2008! Lol. Is it possible at this trucks first oil change somebody covered I guess a semi important sensor? Not sure what kind of change I'm going to see but the lighting and mirrors have definitely been acting wierd on this truck.

View attachment 436427View attachment 436428

ya anything in front of it or even near covering it will make the inside lights dim, not sure if it would cause flickering, maybe if it was seeing conflicting sunsensor readings

 

[solli5pack]

So after doing some testing from the headlight switch I was able to determine that whenever a door is opened and the interior lights come on all the grounds on the truck go to s**t. They go from no resistance at all to over a 100. I close the door, the light slowly dimming to off and the resistance goes down to about 50 ohms then after about a minute I guess the truck goes to sleep and the resistance goes back down to almost nothing. When the truck is running all ground test bad and stay bad....So something is waking up and taking the grounds down with it. Now I just gotta figure out what it is.

 

[solli5pack]

While investigating ground locations I found this module with some ghetto wire repairs. It's the "Rear view camera image displacement module". Anyone have any idea what it actually does? And does it wake up when the doors are opened? Gonna try and get the seat out this week to investigate further.

 

[Fless]

So after doing some testing from the headlight switch I was able to determine that whenever a door is opened and the interior lights come on all the grounds on the truck go to s**t. They go from no resistance at all to over a 100. I close the door, the light slowly dimming to off and the resistance goes down to about 50 ohms then after about a minute I guess the truck goes to sleep and the resistance goes back down to almost nothing. When the truck is running all ground test bad and stay bad....So something is waking up and taking the grounds down with it. Now I just gotta figure out what it is.

Have you tried doing a voltage drop test from the battery terminals to the positive and negative contact points on the engine and the body? Seems like you might have a weak ground or even a positive contact.

 

[solli5pack]

Have you tried doing a voltage drop test from the battery terminals to the positive and negative contact points on the engine and the body? Seems like you might have a weak ground or even a positive contact.

Yes. The grounds all test good until the a door is opened. Then everything goes bad. I'm thinking somewhere inside the truck a voltage source is crossing paths with a ground.

 

[Fless]

Well, if you have a ground that is not able to handle the current ("going to shit") then you likely have a bad cable or ground connection. That's what a voltage drop test would indicate. It's doubtful that B+ is corrupting the ground, but I guess that could happen.

Voltage drop tests on both the positive and negative parts would seem to show any load deficiencies.