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Hello, so I have an ‘05 Cayenne Turbo and the hood open warning light indicator is driving absolutely insane. I replaced the hood latch/hood latch sensor with a new genuine part (955 511 509 02) a few weeks ago. After reassembling everything and getting the hood readjusted took it for a drive and the hood open warning indicator is still on. I readjusted the hood numerous times thereafter thinking that was the issue…but none of the hood adjustments made a lick of difference. So I then figured there was a small chance the new part was defective so I ordered another new hood latch and replaced it again today (not an easy task btw). Well, surprise surprise my hood open warning is still on :-(. I’ve been working on my Porsches and bmw’s for over 25 yrs and I have never been more aggravated than I am right now.
Anyone have any ideas?
Side note: My 955 only has 57 k miles and has been meticulously maintained since new.
If you hadn't already replaced the latch assembly twice, I would have suggested jumpering out the brown wires at the plug. You can see there are only two wires connected to the microswitch from these pics.
The brownish wires. The other red wires are just connected to each other.
So it seems like you have either a bad connection at the plug, maybe a bad ground (?) a broken wire to the control module, a short along the way or a bad module.
Sorry I can't help more.
One thing for sure though, it's not a matter of adjustment. If the hood latches, the alarm shouldn't go off.
Since this module is under the driver's side dash, have you checked the splices under the carpet? (US)
Good battery? Any other electrical gremlins?
Good luck.
Thanks for the suggestions. I’ll double check the brown wires at the plug - they seemed pretty clean and in reasonably good shape though. I thought about jumping the 2 brown wires but wasn’t sure if that would short something out. Not sure where the ground would be located. By bad module do mean the ECU? I don’t have any other electrical gremlins (besides this hood latch issue and also need to replace a high beam bulb - H7 if I’m not mistaken). I didn’t check the spliced wires under the carpeting - not familiar with any factory spliced wires under the carpeting. Are these spliced wires known for having issues? This is the first electrical issue I’ve had aside from replacing the factory backup camera which crapped-out not long before this hood latch issue started. Didn’t really think they had any correlation. I replaced the battery last summer so that’s likely not it.
My wife took it to a Porsche main dealer where they told her the problem was water had entered one of the headlights (which I now see is not working) and it has blown an electronics module.
In the hard to read picture of the schematic, they only show one wire to the "engine hood switch" so the other connection is to the chassis, probably near the latch. I'm just guessing though from past experience.
I have zero experience with any computers on the Cayenne, so I can only tell you what is written on the schematic:
"on board computer network control unit (under left side of dash)"
The wires under the carpet seem out of the way as far as the path from this computer and the hood, but it's basically a 'what have you got to loose' suggestion.
Might be onto something with the headlight module. I’ll try popping off both headlight modules tomorrow and see if there’s any signs of water intrusion. Is it just me or does it appear that the Engine Hood Switch on the diagram is pointing to the Interior Lights System. Anyone know where the “interior lights system” module is located? Worth a look I suppose - even though my interior lights are working fine.
Good eye. So the BLK/YEL wire goes here:
Fig. 60: Overhead Console Circuit
INTERIOR LIGHTS
I got excited at first, but I don't think it's any new info. It's just referring to another page of the main schematic, not another module.
So the end of the line is the microswitch which they call the front flap contact switch.
Another good diagram thesteve! Your second diagram indicates the ground (brown wire) for the “front flap contact switch” is located in the “front left engine compartment”. By “left” side, do they mean driver’s side? I’ll have to try and find that ground in the engine compartment and clean that bugger!
I think I may have found the ground wire. Took it apart and and the contact points weren’t bad but were not completely corrosion free. So I clean the contacts up with a bit of sand paper and lubed them up with dielectric grease. Assuming that is the correct ground I hope this will do it.
Well it wasn’t the ground. Just found the problem. It was the F@&$#*% hood light!!! Was chatting with the wife in the garage (crying on her shoulder actually look for moral support) and it hit me all of a sudden that when the hood latch was in closed position the hood light would stay on but was very dim when it should’ve been off. When I release the hood latch the light got bright. I ended up jiggled the hood light wire when it was dimly lit and the light went completely out (like it was supposed to when the latch is closed). At any rate I cleaned the contacts on the hood light connector and like magic everything works!!! Unbelievable that it was that simple. I cannot help But feel like a moron but at least my wife is taking credit for figuring it out 🙃.
Pretty cool! Ever since I bought my Cayenne, that little light has actually been dangling. Somehow I was never motivated to fix it, I think I couldn't easily see how it was attached.
Your picture explains how it fits from behind. I'll take another look now if it hasn't already fallen off.
Hope your problem is solved for good. It's always reassuring to see on the schematic what is going on, but sometimes things can back-feed or behave in ways you wouldn't predict.
Like the way that "backup horn" is wired... seems something's missing.
Anyway to answer Klaird's question, someone boldly shared a link to a 10,000 page pdf of the service manual. After downloading it, I did not bother to save the url. I just searched now, but came up empty. It's no big secret though.
Maybe someone else remembers the page, it wasn't too long ago.
01-22-2022, 07:27 PM
Hood open warning/Hood latch sensor problem
