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2002 gmc envoy_slt
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15 Posts
Discussion Starter #1
A few days ago our left turn signal started doing the double frequency flash as if a bulb is out.

Things that I can see
1.right turn signal flashes as normal inside, outside front and rear.
2.left turn signal flashes double speed inside, outside rear, but is not flashing the front left.

Things that I have tried is
1.replacing the left front bulb that is not flashing - no changes
2.tested the bulb socket and I'm not getting any power to the turn signal but I do have power to the running lights that share the same bulb.
3.checked the fuses and they were all good.

The only ideas I have are
1.replacing the turn/hazard/towing module GM#12450184
2.replace the tail light distribution boards

I really hate throwing parts at my vehicles hoping to fix an issue so if you have had a similar problem or any ideas they would be greatly appreciated.

Thanks, Fred
 

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2006 chevy trailblazer_ss_lt
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5,895 Posts
since you have a 02, were your tail light boards replaced under recall? may want to contact a dealership and have them run your vin to see if its been done. early boards were plagued by loose bulb retainers
 

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2002 gmc envoy_slt
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15 Posts
Discussion Starter #3
We bought the Envoy used so I don't know if the boards were replaced. I will call the service department tomorrow to see. But if everything is working in the rear lights could it cause a problem with front? Any idea if the 10 pin turn signal module sends a separate signal to the front left and another to the rear left?
 

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2009 chevy
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6,431 Posts
Ok, just to ensure I understand, the left front turn does not work, the left rear turn works (flashes double speed).

Both share the same fuse (#38 rear fuse panel) and the same lead out of the flasher.
This makes me think the flasher is ok.
The rear works, so the boards should be ok (to double check, the left and right can be swapped).
You probably have a problem with the wire going to the front, or the socket at the front.
To check the socket, stick a pin into the wire and check for voltage (it's the light blue wire).
If the socket is ok (no voltage in the prev test), the wire is open between the socket and the rear fuse panel. The pin into the wire will help you find it (note, seal each hole to keep out moisture).
 

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2002 gmc envoy_slt
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15 Posts
Discussion Starter #5
Update #3

RayVoy
that is correct the front left turn signal doesn't come on but the rear does but in double time.

I did what you suggested buy swapping the rear tail lights, business as usual. I also swapped the turn signal bulbs and still nothing changed. I again checked fuse #38 and still no front left light.

I did notice that the small bulb below the turn signal bulb doesn't seem to be coming on, on either side. I will buy two of those tomorrow. What are those bulbs to light??
 

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2009 chevy
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6,431 Posts
I did notice that the small bulb below the turn signal bulb doesn't seem to be coming on, on either side. I will buy two of those tomorrow. What are those bulbs to light??
Clearance lights, parking lights, running lights; any number of names. Basically, they are part of the lighting circuit that is powered when the headlight switch is in the PARK position, or whenever the headlights are on.

In your 1st post, you reported tested for power in the socket, this suggests, to me, that you have a volt meter.
Follow my instructions in my previous post, and you should be able to find the problem.
 

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2002 gmc envoy_slt
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15 Posts
Discussion Starter #7
Turn signal Problem resolved

After hours and hours and a new daughter I finally tossed in the towel and took it to our local GMC service center to see if they could fix the problem. It took them about 2-3 days to figure out that in some point in the Envoy's life the battery had dripped acid on to the wire harness and created tiny tiny holes which lead to the short. They ended up cutting out and replacing 8 wires. They charged me for 3hrs and I believe the bill way $260ish.
 
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