Zaf70

Dear all,

I’ve recently purchased an ‘04 Cayenne S 6 speed manual to go with my 928 GT in Australia. After a day of driving (in heavy rain) it stopped cranking from the key though I am able to get it going and driving fine by shorting the starter relay.

I initially suspected the clutch switch so I swapped it out yet the problem remains. The dash panel however still reminds me to depress the clutch pedal when I try to start it normally even when the switch is activated. Does anyone know if this reminder is triggered only when the ecu detects both a start command and an inactive switch or does it come up automatically every time? I’m guessing it’s the same in all other manual Porsches of the same era.

Btw I did scan it with a generic obd2 scan tool, it had a cam position sensor code which may have been old but didn’t reappear after having been cleared.

thanks,

Jason

Petza914

If you're still getting that message on the dash, the car thinks the clutch isn't depressed. IThat means it's either the switch or the wiring that has to do with the switch. Try jupering the switch or manually holding it down or checking it for continuity in one position and not the other. Since you say this started after driving in rain, you need to lift up the carpets in the front, lift up the insulating pad and check for standing water. I bet everything is soaking under there. Then search for how to repair the splices in the large wiring bundles that run through that area on both sides.

deilenberger

For info on the flooded footwells and what to do about them - see our DIY subforum. Several detailed articles there.

ScootCherHienie

Just a clarification note... if there is water in the padding under the carpet, you cannot feel it by rubbing the top of the carpet, you have to get under the carpet to see if the padding is wet. If you do find wet padding, you likely have plugged roof drains that allow water to run down the inside of body panels where you never see it, before it ends up in the floor of the car that has wiring harnesses running across several parts of the floor. With splices and connectors under there, you can experience shorts to ground that can prevent signals from working as they should, even if the switch is good. There is a lot of info on roof drains in the DIY section of this sub-forum. Typically all that is needed to fix water infiltration from the roof drains is removing the little slip-on caps and let the water run out. Some people do not reinstall the caps since they cause the problem in the first place. This is not unique to Cayennes. A dealer shop in a used luxury car dealership said backed-up roof drains are a problem for many brands of car and SUV. Water in the carpet padding is also a common source of battery drain problems when the battery won't stay charged for more than 4 to 10 days at a time. Once you have released any backed-up water in the roof drains, 100% of your problem(s) may disappear once you have dried the interior... which can take a long time in cold weather. I dried my carpets in 3 days without fans in the summer over 3 days with the Cayenne in the driveway all day with doors, windows, sunroof, and rear hatch open. Outdoor temps were close to 100 degrees in the hottest parts of those days. I have no idea how much longer it would take to dry-out in colder temps, even just 50 degrees F would slow-down the drying considerably. Equipment rental businesses often rent drying fans which can help a lot if the humidity is low enough. I dried the padding on those hot days without lifting the carpet, a tricky job in a few places, but if you need to dry the padding fast and the weather isn't cooperative, lifting the carpet (not removing it, but raising it 6 inches or so to allow a fan to circulate are between the bottom of the carpet and top of the padding). If the water under your carpet has only been causing this problem since it rained, there could well be NOTHING NEEDED in regards to repairing the wiring harnesses or connectors. Dry everything out, drain the roof drains and leave the caps off and you could possibly not need to do anything else.

Zaf70

Wow, thanks for the detailed responses. I’ve lifted up the carpets on both sides but it looks bone dry and there seems to be no evidence of water ever having gotten into the wiring there but I think I may have found another possible culprit.

I did some more reading on 911 forums as they apparently have a similar clutch set up and have numerous threads on clutch switch failures. It turns out there are 2 clutch switches, the second one is very hard to see and next to impossible to reach without removing the clutch pedal. I’m going to try to find a way to bypass the switch to confirm that’s the issue. I let you know how I go.

Thanks again!

Petza914

My fault. I should have mentioned that to you. The easy to access one is not the one that requires you to push the clutch in for thstrting the car. It's the upper one that does that as well as disengaging the cruise control. The lower one retards the timing of the engine as its being let out to prevent poor manual drivers from stallion their cars. In fact in our 997s I've jumpered that lower switch so it never does this and the behavior of the engine when letting the clutch out makes for a much more linear experience withiut the "farting" sound that occurs.

That's great news that you don't have water ingress. It's the upper clutch swot h you nedd to change and then you should be good.

Zaf70

Ok great - I guess what that means is that if I bridge the 2 wires the cruise control will cease working as it will always think the clutch is in?

Petza914

You'd also be able to start the car with the transmission in gear and the clutch not pressed in, which isn't all that safe, but yes, you could test it that way and maybe even use it that way while waiting for the part to arrive.

Zaf70

Great news - I bridged the clutch interlock switch and it worked! Thanks for all your help, I love the car but that issue was driving me a bit crazy.

When I went to remove the plug from the switch the brown wire immediately detached, I suspect it cracked somehow. I’ve ordered a new switch but it’ll have to wait a bit for it to arrive.

I guess one of the issues with having an unusually specced Cayenne is finding information, the wiring diagrams I had didn’t show the interlock switch though they showed the other clutch switch. It looks like a purple/black wire sends 12v to the interlock switch from the driver id module then the activated switch sends 12v to the ecu which in turn activates the starter relay. Anyway, that’s why this forum is such a great resource - to find help in sticky situations.

Thanks again!

deilenberger

Thanks for coming back and telling us the resolution to the problem - that makes the thread useful for someone with the same problem in the future.

Petza914

That's great. Congrats.