I have a 2008 911 C4S Cabriolet (997.1).

Passenger side tail light blinker fails 100% of time when engine is running and lights are off.

It fails frequently when engine is running and lights are on.

It never fails when engine is off and only power is on.

Resistors were added to the aftermarket LEDs (front and back) but didn’t solve the issue. I probably didn’t need to do this because I don’t have a Turbo.

I notice the (unnecessary) incandescent fog bulb on the passenger side is seemingly fused into place and it can’t be removed. It won’t allow me to push it in, let allow me to twist it. This is not the turn signal bulb (which is LED), but perhaps it’s worth mentioning.

Similarly, the driver’s side incandescent fog light bulb is stuck. It at least allows me to push it in, but it won’t twist out. Driver’s side taillights and blinkers work fine at the moment so I’m not overly worried about this at the moment.

Two questions:

1. Is there a turn signal “relay”in the 997.1? Or is it simply part of the Body Control Module (BCM)?
2. If yes to #1, where can I find it? I’ve already looked near the fuse box in driver’s footwell—it’s not there—and I tried to look below the VIN plate via the frunk and I don’t see it there either. Could it be behind the speedometer on the dashboard?!? I’ve read 100s of posts and can’t find whether this turn signal relay truly exists for a 2008 (997.1). Frustration level 11.

Side note 1: I have a new wire harness on the way, in case there’s something wrong with the wiring.

Side note 2: I’d LOVE to switch to OEM incandescent bulbs (and eliminate this nonsense), so if you have the OEM housings for sale, please let me know!!

Thank you for any advice you can offer!

Best,


Jay

 

Disconnect the electrical connection at that taillight. With some needle nose pliers, grab each pin and pull it toward you to make sure all of them are fully seated into the connector. Now take a wire tie and wrap the whole bundle of wires tightly right where they enter the plastic connector. When plugging the two sides of the conne tir together, wiggle them a bit as you click them in.

What happens if one of those pins doesn't perfectly line up with the female hole and it gets pushed back in the connector making intermittent contact. When the car is sitting still it works, but when it hits bumps or vibrates it's losing contact and throwing the code.

Also I'd the taillights are some of brand like Spyder, they just fail. I had Spyder lights on my car when I first got it and the passenger side light would go bad every 30 days and thed send me a new one. Got tires of it and bought Depo/Dectane and no more failures on either car - that was 12 years ago. Have Morimotos on now and no issues with those either

 

Thank you for this, Petza914!
I’ll try this today and report back. Note:

I installed the Morimoto’s last week and observed the same issue, so I don’t think it’s the actual tail light.

For the pigtail connector, I noticed that the passenger side only has 5 wires, thus 5 pins in the 6 holes. I believe this is due to passenger side not having the fog light wire, but if you believe a 6th pin is crucial, then I’ll install a new one when it arrives this week. See pics below.

I’ll also use the new wire harness that arrives this week because that will give me a chance to ensure that wires/LED bulbs are configured correctly, though I’m not sure how the previous owner could have messed that up.




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​​​​​​​Rear fog light is only on driver's side and why the wire difference

 

UPDATE (3/31/25): Still no luck. Here’s what I’ve found so far:

-Likely not the ‘08 C4S not liking LEDs since drivers side and front LEDs are working fine
-Likely not the aftermarket LED taillight since I bought new Morimoto LEDs and passenger side blinker still fails
-Likely not the passenger side rear wire harness; I replaced it yesterday with a new one and get same results
-Likely not the flasher relay since the blinkers/hazards work fine when engine is off and when the right taillight is removed entirely The blinker ONLY fails when the passenger side taillight is in and I’m driving. It works as expected when the engine is not running.

Next step—unless anyone has any better ideas (I’m all ears!)—is to:

-Replace the pigtail connector that Petza914! referred to with a new one (see pic below). I don’t love this idea because I need to splice into the wires in the vehicle. That said, even tweezers (let alone needle nose pliers) were too big to get into the holes on the existing pigtail connector to ensure all were extended properly.

If I replace the pigtail connector and it doesn’t resolve the issue, I assume the problem is further up the line (and above my pay grade).There is something called a Turn Signal Flasher Lamp Blinker Module Control Unit (99761820100) that I probably don’t want to mess with.

Before I start splicing in this new pigtail connectors, does anyone have any more ideas? Thank you in advance!

 

It's the pins on the other side of that connector that gets pushed out and then don't make with the one you pictured properly or completely. However, with 2 different sets of taillights, it's probably not that.

I would do a test where you reinstall the original, non-LED taillights and see if you have the same issue as that will help narrow things down.

 

Thanks for this. I actually replaced the wire harness yesterday with a brand new one. The wire harness (with the pins) connects the LEDs to that pigtail connector. So, I feel like I narrowed the issue down to upstream of the tail lights and wire harness. I wish I had OEM taillight to test, but I don’t. The brand new Morimoto’s had the same issue—only on the passenger side. I really don’t think it’s the LEDs.

The pigtail connector is likely next. That said, if you or anyone know if the 2008 911 C4S (997.1) has a flasher relay and where that might be, that would be helpful. I don’t see it above the fuse box and I don’t see (or hear) it beneath the VIN plate from the frunk. Is it behind the speedometer/tachometer on a 997.1?

Thanks!

 

I tried to look this up on an old PDF wiring diagram and was thwarted by low resolution.
I did find that at least one submodel used a control module for controlling turn signal flashing. 99761820100
I think there are relays in at least two spots in the car. Driver's footwell and under rear seat/rear shelf, methinks. Other search results showing the fuse box and relay box diagrams suggest there's no "flasher" used.

 

Thanks, John. Yes, I found that, too (99761820100). I might leave it to the professionals to replace that!

 

Update (but can still use support):

I brought the car to Rennwerke Porsche Technicians in Elmsford, NY. Turns out I needed a new Lamp Control Module. All my blinkers now work 100% of the time on the outside, but I still get a hyper flash on the dashboard with the left directional. Again, the blinkers work correctly outside the vehicle—the hyper flash is limited to the dashboard.

I have a 2008 CS4 (not a Turbo), so I don’t think resistors are necessary.

Any thoughts from someone with this issue?

 

You might try temporarily swapping the lights side to side to see if the hyperflashing follows the light.

 

Good idea. I did that when trying to diagnose my previous blinker issue. I shall try that again. Thank you!

 

So, I removed the driver’s side taillight from the wire harness and I still get the hyperflash on the dash. (Front blinkers flashed normal.) Then I unplugged the passenger side taillight and I got the hyperflash there, too. (I didn’t swap driver’s side and passenger side because the driver’s side has a rear camera wire spliced in and I didn’t want to deal with removing it.)

I’d love to replace these LEDs with OEM/incandescent tail lights, but don’t want to buy them without being sure that will solve the problem. Essentially, still at square one.

 

To test the theory "will incandescents solve the hyperflashing", you could temporarily wire in incandescent bulb sockets. Or, less hackish, find a new raw plug and then adapt the bulb socket to it. Or maybe there's enough conductor exposed on car's connectors plugs to jam in the bulb socket leads to make a good connection.

 

Sadly, both of those options are above my pay grade. Asking a fellow Porsche owner to steal their tail light for 5 minutes might be possible though!