XCM

Gurus,

Not terribly optimistic but wonder if some guru here has a solution. In a nutshell my 2008 Cayenne S was originally spec'ed with Xeons but both headlights have now been downgraded to HID. I believe that car still thinks it should have Xeons so I'm getting "System Fault Headlight" error on the dash. I wonder if there's was a way to reprogram it to tell it to look for HIDs instead and therefore no long shows the error. For a bit more detail I'm get the following errors from a scan tool:

15582 Left headlight
2498 Cover for left dipped beam headlight
2589 Bulb for auxiliary high beam headlight, left

Headlights work so not a big concern to me but would be cool to get rid of the error code.

As for a bit of background as to how this came to be: Long story but bought my 2008 Cayenne S use recently. It originally had Xeons but when I bought it one of the Xeon headlights had recently been changed to a HID headlight. I suspect it had an issue when the dealer took it in and rather than go through the expense of sourcing a Xeon they took the cheaper road of replacing with a new OEM HID. I suspect they weren't aware that would throw an error and by the time they realized they were stuck with that setup. I was aware of the mismatch and error when I purchase the car and got a good discount on account of it.

My plan was to sell the used Xeon, get a new HID to match the new one and then change both to LED bulbs for a nice modern light. That part of the plan worked out well but as suspected the error message on the dash remains.

BTW for anybody interested in the LED part of this story here's a few pictures of the conversion. Was a bit of a chore to get LED bulbs to fit inside the retaining clips (had to order new aftermarket ones) but I'm really happy with the lighting.


As I got the car. Driver side is new HID and passenger side is original Xeon.


LED in the HID housing on Driver side and original HID in passenger side (that one was post picture changed to HID w LED to match). Really like the LED in there.

Thanks!

deilenberger

I'm afraid you're confusing terms:

"XEON" is an often used generic term for different sorts of headlights. Usually used to try to pretend halogen lights are the same as HID lights.

"HID" is the abbreviation of high-intensity-discharge light sources. Basically an arc-lamp with an electrical spark between two electrodes producing a white appearing light (or blue depending on the gas mix used in the bulb capsule.) These need a high-voltage trigger to fire off, and a source of higher than 12V (usually around 38V) to continue the arc once it is fired. So they need ballasts to work. These are MUCH more expensive than a halogen light. And far superior in light quality/distance.

It sounds as if your vehicle may have originally been equipped with HID lights, and the dealer took the cheap way out and ordered a halogen setup for the replacement. But given your description - I'm really uncertain what you have.

Am I correct in assuming that the back of the two lights appear different? The HID one will have the ballast screwed to the back of the light.

If so - you have to decide what you want to do. If you really want to go the LED route (I'll explain why this isn't a great idea in a second..) you would be best served buying another halogen housing and installing LEDs that are supposed* to replace the standard bulb. That shouldn't require any drastic changes in wiring, although if the LED replacement isn't listed as "CAN-BUS" compatible - it may result in a headlight out error appearing.

What the "CAN-BUS" compatible ones do is add a resistor across the LED bulb to simulate the current that would be drawn by a standard halogen bulb. The light control module measures the current being drawn, and if it is too low it assumes the bulb has a lack of continuity (ie - burned out) and triggers the warning. The resistor and the LED's will still generate about the same amount of heat that the standard halogen bulb would - so placement of the resistor is important, as is cooling for the back of the LED module (usually has a finned back to help cool them.)

The alternative would be to get another HID light assembly (they appear on Ebay frequently, but often without the ballast which can be pricey) and have two HID headlights. That's probably the best lighting you can expect to have.

Now - the story on LED replacements.. in order to provide the same light output that a standard halogen bulb will - the LED has to have active elements located in the same location and exact size of the halogen filament. This is basically impossible - but some of them at least try. If this doesn't happen - the beam shaping optics of your light will not be able to create an effective beam pattern from the LED. It might very well create scatter and blind oncoming motorists.

On the HID lights - there is a single HID light source - with a shutter that opens and closes for high and low beam.

Usually on halogen lights - the bulb will have two filaments - one for high beam and one for low beam. The inner light elements also may be used for high beams, effectively giving you 3 light source (low, high, high) when the high beams are used. There is no way to replicate this with an LED replacement module.

The error codes you're seeing are because the light control unit is expecting HID headlights (with the shutter - that's the code 2498) and isn't finding it on the left side.

Replacing the right side with the same headlight as the left side has (with the LED module) will result in the same codes appearing for that side. You can have the dealer perhaps switch off the setting in the light control module that tells it there are HID's attached - and that might clear the codes. That might also be doable with the Durametric professional diagnostics tool (which can do some programming) - but that's an expensive tool.. I'm not sure if the iCarScan tool (lots less expensive) can do that since I haven't tried it (and I no longer own a 955/957 series.)

Good luck!

XCM

deilenberger,

Thanks for the post. Fair point that terminology might not be clear. To clarify:

My car came from the factory with what Porsche calls Bi-Xeon
Before I purchased it one of the Bi-Xeons headlight assemblies was replaced with a halogen assembly.
After my purchase I've replaced the other Bi-Xeon assembly with a halogen assembly and changed the bulbs in the halogen to LED.

Trying to figure out if there's a way to re-program the car do believe it should have halogens and thereby clear the errors.

Thanks!

PS I've already installed the LEDs so too late to change that. The LED market is a total jungle but I'm happy with the light pattern, intensity and color. Maybe I just got lucky but I'll take it.

deilenberger

The "Bi-Xeon" is an HID light with a moving shutter for hi/low.

You've now installed halogen assemblies and LED bulbs.

Your dealer can program the light controller to think it has halogen bulbs. That should clear the error related to the "cover" (shutter).

The other two errors are bulb errors - and it depends on if your LED's have a resistor to fool the bulb monitoring circuit. If not - it is probably possible to add one and eliminate that error message.

XCM

Hi deilenberger,

Thanks. Will be interesting to see if the deal can repogram. I do have a ICarScan so might poke around in there but doubt that can do it. Good to know on the bulb errors. Those are from before the bulb change so will have to clear and see if they come back. Thanks for the help.

mudman2

No amount of re programming ever fixed my error (on the 04)

XCM

mudman2, thanks .. figured but never know if somebody out there has figured it out. Not much online regarding the subject. Probably because very few people downgrade from the Bi-Xeons. Thanks.