C7 Mathis

Hey guys,
Sorry if this is a repeat question but I tried searching for a while and couldn't find anything.
I just replaced the left front turn signal bulb with a Sylvania 3157NA/4157NA and the DRL is fine. The problem is that the turn signal noise is still fast and the light won't blink. Is there a Signal / Hazard flasher unit somewhere behind the dash? A lot of the info ive seen looks like for a C5. Any ideas what the issue could be? Is it definitely not a bulb / housing issue since it lights up? Any guidance would be awesome. Thanks guys!

Knob Jockey

There is no turn signal flasher to replace, they are controlled by computer.

Since the DRL and turn signal use the same circuit, connector and major filament in the bulb, it's unlikely that one would work without the other.

The turn signals will hyper-flash whenever a lamp is out and as you said, the light isn't blinking.

When you said the 'the DRL is fine', are you sure you aren't looking at the minor filament lit up, that is the parking/running light?

If your diagnosis is correct, the computer (BCM) may be faulty. Which means a trip to the dealer.

I'd check the socket and make sure there are no dirty or burnt contacts and that the wiring harness is not damaged/pinched.

MikeyTX

Did you check for a burned out rear bulb ?

C7 Mathis

Okay so I think I said it wrong. When I manually turn on the orange driving light the bulb turns on. When I try to use the turn signal or press the unlock button the bulb does not flash

I guess that what you're saying is that the car is not accessing the major filament? Is controlled by a flasher unit or all computer managed? I can check the socket again and make sure it's clean. Would you guess it's definitely not the bulb if the minor filament is working on both new ones I tried??

FortMorganAl

Yes. There are 2 filaments. Yes, it is controlled by the BCM (a computer) and it is doubtful the BCM has failed but certainly possible and expensive. If you have tried 2 new bulbs (3 including the original failed one) then hope that the issue is in the socket. An out of warranty repair could get very expensive.

But just because one filament works doesn't mean both are good. You could try another bulb or a $10 voltmeter from Radio Shack would tell you the condition of the filaments by measuring the resistance. You could also use it to tell if the BCM is sending voltage to the socket.

Finally, the rear filaments have nothing to do with this issue. Even with a rear bulb out the front will still fast flash. The GM engineers were smart enough to know not to disable all turn signals when a single filament failed.

C7 Mathis

Okay so it would be really hard for me to believe that it's a computer issue. It seemed at the time like any other typical blown bulb. Is there a relay or fuse that I should look to change?? I'm having some work done at the dealer next weekend but wanted to check all the minor issues before I ask them to look at it. I can check the socket again to make sure it's clean before I take it in.

Thanks guys, any more ideas?

C7 Mathis

Here's another update. The old bulb looks intact after a second look. I didn't even think to check as I assumed it was a dead bulb.

Assuming the computer is okay (for now) is the best guess that it's the socket or the socket wiring?

Thanks again

FortMorganAl

If all the other lights work then it isn't a fuse or relay. I agree that a computer problem is unlikely and that it is more likely a socket issue.

Again I'll recommend getting a cheap voltmeter. Makes troubleshooting a lot of all home/car electrical issues a lot easier and can last a lifetime. You don't need an expensive accurate one. Just basic ballpark voltage, current, resistance.

Zoxxo

You could try installing the known good bulb (from the other side) into the questionable socket...

Z//

MikeyTX

Ding ! We have a winner ...............

larryrs

Did you ever find a solution? Now my right side DRL will not flash with blinker on. I replaced the bulb (which looked good) with two known good ones and still no flash from front right DRL. My socket is clean and looks very good for a 10 year old vehicle. I plan on tracing the wires back if I can. Does anyone have any knowledge of this issue and what I should be looking for?

heydutchie

Larry - any luck figuring out a solution? Mine just started doing this, too.

larryrs

The problem with mine was the socket was burnt and corroded. I scraped the connectors where the bulb plugs in and it started working again. Meanwhile on eBay, there is a fellow selling the oem socket wiring harness. I ordered 2 of them to replace both when the time comes.

heydutchie

Thanks for posting that....I'll give it a try.

Ursoboostd

My right DRL/turn signal is not working. Looks like I have this problem also. My driver headlight assembly has been a little foggy for some time now. I'm guessing that came from the heat of this bulb. Ugh.

veloz

replace the socket,,,i pigtail mine in, problem solved...i didnt replace the whole harness like others do..