hotrod2448

I had an odd situation yesterday and I’m trying to determine if it is likely to repeat or if it is indicative of a looming problem.

I daily my CD so it sees regular use. It does not have keyless go so now sensors on door handles. Yesterday while having already made multiple stops where we locked unlocked the vehicle without issue, we made another stop in a parking garage. I hit the lock button and no chirp. I’ve had the door lock actuator failure where the vehicle doesn’t lock or arm the alarm before so, I wasn’t really concerned about that.

Opened/Closed the doors, hit the button again, doors locked, chirp chirp, all good. Go into the store come back out, hit the unlock button… nothing. Check the car, doors are locked, alarm lights are flashing. Hit unlock about 50 times while walking around car, no change. Tried relocking, tail gate, etc… nothing.Key fob light is flashing with button push, battery was changed in the key about a month ago and has been working fine. Finally after about 5 minutes of button pressing and swearing while walking around the car it unlocked and has been fine over a few additional stops.

I’m wondering what the likely causes of this issue are. I’ve come up with the following so far:
1. Localized RF interference, wondering if there is something in the garage that could interfere with the vehicle receiving signal from the key. I feel like I have noticed reduced range in this garage previously but, never outright inability to function.
2. Indication of vehicle battery needing replacement (roughly 5 years old now)
3. Alarm battery, I’ve read a little bit about this, unsure if it can have this kind of effect.
4. ???

Anything else I should be considering or thoughts on how to identify likely root cause?

hotrod2448

Also worth mentioning the actuator failure was a few years ago, was replaced and has functioned perfectly since.

garrett376

Likely interference. It happens...

CAVU

Op,

Sounds like what happened to me several years ago. https://rennlist.com/forums/cayenne-...g-to-fail.html

hotrod2448

Not sure about that. My understanding is the alarm siren failure doesn’t prevent the vehicle from actually locking and unlocking unless there is something I’m not seeing.

Leaning towards interference but it’s just weird that in 6+ years of ownership it’s never happened before.

garrett376

Over the past 6 years, do you frequent that same parking garage where it occurred? Even if you do, what's not to say there is a new tenant that may have a new "whatever" that emits interference, or an old tenant that happened to be creating interference this one time you were there. Or, did you park next to an Agency vehicle? Too many what-ifs with a known issue; I wouldn't worry about it; interference happens with these, and that's a reason you have a manual way to enter the vehicle!

CAVU

I do not know for certain.

I was several times temporarily locked out with symptoms like yours. After looking at the wiring diagrams and the internals of the anti-theft alarm siren, the car was 10 years old (seems to be the life limit for its internal battery, and the wife is the primary driver, I replaced it as preventive measure, not curative. I have had no issues since but I can not conclude that I found the fault. I had not considered interference/location until Garrett mentioned it in this thread

To this non-electronics eye, there seems to be a lot going on inside that siren box based on the pictures in the link I posted.

Garrett has a lot more experience than I do with cayennes. A trustworthy source of info.

Daveheardt

This might sound stupid but ... have you tried changing the battery in the key fob with a different one? I understand yours was changed a month ago but there are faulty batteries on the market, it happens. When I bought my 2011 CD (<1 month ago) I changed the battery in the fob within an hour of purchase as the old one was quite flat. Yet, 1/3 of the times the car wouldn't unlock doors properly. I was panicking thinking I bought a car with "hidden issues" but after I changed the battery again the problem was resolved and I haven't had it since.

EDIT:
Nevermind, I slightly missed this part of your last post