2007 Tahoe - Blinker Flashes rapidly after 3 times normal

[DJPoertsch]

Dear friends.
I have a problem with my turn signals on my Tahoe 2007.

Blinker issue while driving and park. Blinker Flash rapidly after 3 times normal.

If I press the right turn signal when the engine is running, it flashes 3 times normally and then gets fast flash mode. The left turn signal works normally. None of the bulbs are defective. In the back I have installed LED lights in Cadillac style. If I turn off the engine and leave the key on ignition, then the left turn signal did the same as the right one 3x slowly and then quickly.

When I now turn on the hazard lights, all the turn signals at the front, those in the mirrors and at the rear flash normally. I read that the turn signals are controlled by the BCM and there are no relays as such in the Tahoe. Is that right? Or do I have to replace the whole BCM here. That would be completely stupid. Do you have any ideas what I could do and how to solve the problem. Thank you very much

 

[kbuskill]

The LEDs are causing it to "Hyperflash" because the BCM thinks there is a bulb out because the LEDs don't draw as much amperage.

You either need to install resistors or find someone to reflash the BCM with an LED compatible program.

 

[DJPoertsch]

The LEDs are causing it to "Hyperflash" because the BCM thinks there is a bulb out because the LEDs don't draw as much amperage.

You either need to install resistors or find someone to reflash the BCM with an LED compatible program.

Thanks for the hint.
But here I have to disappoint you, because I have installed the LED lights in the back of the car for over 4 years now. I have installed special resistance, they are included at the lights, when I was getting the lights from US to Germany. They are the big Cadillac Escalade Taillights. If there were a resistance problem, the Blinker would flash quickly at any time. But they only do it as I described above. When the ignition and engine running, quick flashing runs on the right after 3 times normal flashing. If the ignition is on, but the engine is off, the left turn signal also flashes quickly after 3 times normal flashing. At warning indicators, everyone flashes normally. There can't be any resistance Problem. I am an electrician and will connect my tester (Kingbolen K8 Pro) and read all control units. Maybe something will be shown here.

I hope that possibly someone here had a similar Issue like mine here.

 

[DJPoertsch]

Next step would be

I will try first all those simple Issues that could be. I order some new Bulbs but no LED. They are not necessary in Turn signal lights. So i order 4 Standard bulbs, 2 for spare.
Then i will check the connector and the Ground. If this steps are done then i will check all again, if my issue still there or it is gone. If it works then perfect. Great I am happy. If not i will go into the next step, to find the issue and burn my Tahoe

 

[Joseph Garcia]

I kept the hyperflash, because it is more noticeable to other drivers on the road around you, and isn't that the purpose of a directional after all? I will note that hyperflash is illegal in some states, though.

 

[kbuskill]

Thanks for the hint.
But here I have to disappoint you, because I have installed the LED lights in the back of the car for over 4 years now. I have installed special resistance, they are included at the lights, when I was getting the lights from US to Germany. They are the big Cadillac Escalade Taillights. If there were a resistance problem, the Blinker would flash quickly at any time. But they only do it as I described above. When the ignition and engine running, quick flashing runs on the right after 3 times normal flashing. If the ignition is on, but the engine is off, the left turn signal also flashes quickly after 3 times normal flashing. At warning indicators, everyone flashes normally. There can't be any resistance Problem. I am an electrician and will connect my tester (Kingbolen K8 Pro) and read all control units. Maybe something will be shown here.

I hope that possibly someone here had a similar Issue like mine here.

I will almost guarantee there is a resistance problem somewhere, either in the front signals or the built in resistors in your tail lights are going bad.

The 3 flash normal then hyper flash is standard operating procedure for the BCM, so is the normal flash rate for the emergency flashers.

I would get out your multimeter, unplug your tail lights, and check the resistance value on the turn signal wiring at the tail lights themselves to verify the built in resistors match from one side to the other.

Since you are an electrician, perhaps you have some spare resistors laying around (50W 6 OHM) you could install on the trucks wiring in place of the tail lights as a test, or if you have the old tail lights laying around just plug those back in for testing. This will at least verify if the problem is at the tail lights or not.

 

[DJPoertsch]

I will almost guarantee there is a resistance problem somewhere, either in the front signals or the built in resistors in your tail lights are going bad.

The 3 flash normal then hyper flash is standard operating procedure for the BCM, so is the normal flash rate for the emergency flashers.

I would get out your multimeter, unplug your tail lights, and check the resistance value on the turn signal wiring at the tail lights themselves to verify the built in resistors match from one side to the other.

Since you are an electrician, perhaps you have some spare resistors laying around (50W 6 OHM) you could install on the trucks wiring in place of the tail lights as a test, or if you have the old tail lights laying around just plug those back in for testing. This will at least verify if the problem is at the tail lights or not.

Thank you so much for all your tips. I'll try them out. But one question remains. Why do all the indicators flash normally when I turn on the hazard lights? They all flash as they should. None flash quickly.

 

[kbuskill]

Thank you so much for all your tips. I'll try them out. But one question remains. Why do all the indicators flash normally when I turn on the hazard lights? They all flash as they should. None flash quickly.

Standard programming in the BCM.

 

[PatDTN]

I read this thread through because I bought a well used '07 Silverado and have the same issue with just my left turn signal. My truck is all incandescent bulbs. Any thoughts on how that can happen? All the bulbs flash as they should. I did replace a burned out bulb in the left rear light when I got the truck in Feb.

 

[Fless]

I read this thread through because I bought a well used '07 Silverado and have the same issue with just my left turn signal. My truck is all incandescent bulbs. Any thoughts on how that can happen? All the bulbs flash as they should. I did replace a burned out bulb in the left rear light when I got the truck in Feb.

Was the new bulb the correct part#? I would bet that the BCM is aware of the current draw, and a wrong bulb might trigger it.

Swap the left and right bulbs and see what happens.

 

[PatDTN]

Was the new bulb the correct part#? I would bet that the BCM is aware of the current draw, and a wrong bulb might trigger it.

Swap the left and right bulbs and see what happens.

Sounds like a good start! Thanks.

 

[JD12]

i have the same issue, and my guess is bcm….i’m at 231k, and the bcm is finally on the fritz…all the following symptoms are occurring within the same week i installed a new agm. no hvac blower in front, back works fine…three windows won’t function, back right window only one working…door lock/unlock switch failed, front dome light buttons failed (works fine with door open or dash button)…left rear turn signal fail, mirror signal was fine, now both mirrors fail turn signal…

i just cleaned the undercarriage grounds and retightened, plus dielectric grease…tightened underhood grounds…going to clean the bcm connections and check the interior grounds tomorrow

 

[DJPoertsch]

Hello everyone.

I have found my problem.

Firstly, I had to replace the steering column stalk for the turn signals, because I had the typical flashing of the high beam when I turned on the indicator. But that wasn't the problem here either.

As you know, I have Cadillac taillights installed. There is a resistor for the turn signals installed here. A slightly larger black box. This is where the resistor is installed. I realized that it was broken when I connected my caravan to my trailer hitch. As soon as the plug was plugged in, the rapid flashing stopped. Since I am an electrician, I was able to quickly determine that resistors are subject to aging. I then got hold of 50 ohm resistors and swapped them for the original resistor box and lo and behold, it worked.
The BCM itself reacts to a change in internal resistance. If you can measure the current going to your LED bulbs, you can quickly calculate how many ohms you are missing, in order to then use a resistor connected in parallel to achieve the value produced by a standard light bulb. You will see, it works. But I would test it with a trailer, or you could build a small test lamp that you connect in parallel to the terminals between V12+ and V12- of your defective Light Bulb (hyper flash) . This also increases the resistance and allows you to rule out a defect in the BCM. The BCM itself is equipped with a resistance meter, which ensures that a defective bulb is indicated by rapid flashing. 99% of the time, it's not the BCM. Best regards, Markus from Germany.

 

[mikez71]

Odd you were getting 3 normal blinks..
I guess that heated up the resistor enough to change it's resistance.

Thanks for the update!

Upload vehicle pictures if you get a chance...
Looking at your profile picture, I am guessing your truck is lowered..

 

[DJPoertsch]

If someone like to see how my Tahoe Looks Like. Here some Pictures.
Now lowering all Standard.
Its the best car I even drive.. Actually build 2007. 424000km with 1 Motor and 1 Gearbox. Its an LTZ with 3 Seats in Front.. I have an Flow master under it. And ist still a nice Daly driver.

 

[PatDTN]

Odd you were getting 3 normal blinks..
I guess that heated up the resistor enough to change it's resistance.

Thanks for the update!

Upload vehicle pictures if you get a chance...
Looking at your profile picture, I am guessing your truck is lowered..

I don't know how it relates to the lane change but my Silverado is doing the same thing. Three normal blinks then rapid flashing. All my bulbs are standard incandescent.

 

[kbuskill]

Hello everyone.

I have found my problem.

Firstly, I had to replace the steering column stalk for the turn signals, because I had the typical flashing of the high beam when I turned on the indicator. But that wasn't the problem here either.

As you know, I have Cadillac taillights installed. There is a resistor for the turn signals installed here. A slightly larger black box. This is where the resistor is installed. I realized that it was broken when I connected my caravan to my trailer hitch. As soon as the plug was plugged in, the rapid flashing stopped. Since I am an electrician, I was able to quickly determine that resistors are subject to aging. I then got hold of 50 ohm resistors and swapped them for the original resistor box and lo and behold, it worked.
The BCM itself reacts to a change in internal resistance. If you can measure the current going to your LED bulbs, you can quickly calculate how many ohms you are missing, in order to then use a resistor connected in parallel to achieve the value produced by a standard light bulb. You will see, it works. But I would test it with a trailer, or you could build a small test lamp that you connect in parallel to the terminals between V12+ and V12- of your defective Light Bulb (hyper flash) . This also increases the resistance and allows you to rule out a defect in the BCM. The BCM itself is equipped with a resistance meter, which ensures that a defective bulb is indicated by rapid flashing. 99% of the time, it's not the BCM. Best regards, Markus from Germany.

The LEDs are causing it to "Hyperflash" because the BCM thinks there is a bulb out because the LEDs don't draw as much amperage.

You either need to install resistors or find someone to reflash the BCM with an LED compatible program.

I will almost guarantee there is a resistance problem somewhere, either in the front signals or the built in resistors in your tail lights are going bad.

The 3 flash normal then hyper flash is standard operating procedure for the BCM, so is the normal flash rate for the emergency flashers.

I would get out your multimeter, unplug your tail lights, and check the resistance value on the turn signal wiring at the tail lights themselves to verify the built in resistors match from one side to the other.

Since you are an electrician, perhaps you have some spare resistors laying around (50W 6 OHM) you could install on the trucks wiring in place of the tail lights as a test, or if you have the old tail lights laying around just plug those back in for testing. This will at least verify if the problem is at the tail lights or not.

Odd you were getting 3 normal blinks..
I guess that heated up the resistor enough to change it's resistance.

Thanks for the update!

Upload vehicle pictures if you get a chance...
Looking at your profile picture, I am guessing your truck is lowered..

Standard programming in the BCM.

Strange, almost like someone knew what they were talking about... lol

 

[mikez71]

You were right! (I thought BCM was a good guess too whoever said it)
Oh, did you mean with wrong resistance, the BCM will still do 3 normal blinks before hyperflashing?
I just took your statement to mean the hazard switch bypasses the hyperflash programming.

Now figure out @PatDTN 's same issue with normal bulbs!

I would say he swap bulbs or get new ones first.
Possible the old front bulb is about to go.

Ok Just googled it (actually bing'ed it) incandescent bulbs change resistance with temp, less when cold, more when hot. I am guessing more-so if the bulb is old and filament has a thin spot. Check socket and wiring while you change bulbs.

 

[kbuskill]

Oh, did you mean with wrong resistance, the BCM will still do 3 normal blinks before hyperflashing?

Correct.

Another interesting tidbit of info is that if you just tap the turn signal stalk, without going passed the detent, the turn signal will flash 3 times and go off.

But if you are connected to a trailer and do the same thing, the turn signal will blink 6 times before going off.

 

[kbuskill]

Now figure out @PatDTN 's same issue with normal bulbs!

Same issue. Bad bulbs or bad connections.

The Silverado uses both upper and lower bulbs in the rear for turn signals and brake lights, so it is important to check both. Where as the SUVs use the top bulb for brakes and the bottom for turn signals.

Unless you are me and have rearranged things to work differently... lol

Also, as a side note, the Avalanche is essentially a Suburban body and chassis but it is wired like the Silverado so both bulbs are dual purpose brake/turn. Just an interesting bit of trivia in case you are ever on Jeopardy and get asked.